Pierre-Louis Maupertuis (1698–1759)

Source: Wikipedia

Pierre Louis Moreau de Maupertuis was a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Prussian Academy of Science, at the invitation of Frederick the Great. His work in natural history is interesting in relation to modern science, since he touched on aspects of heredity and the struggle for life. Some historians of science point to his work in biology as a significant precursor to the development of evolutionary theory, specifically the theory of natural selection. Other writers contend that his remarks are cursory, vague, or incidental to that particular argument. Mayr's verdict was "He was neither an evolutionist, nor one of the founders of the theory of natural selection [but] he was one of the pioneers of genetics". Maupertuis espoused a theory of pangenesis, postulating particles from both mother and father as responsible for the characters of the child. Bowler credits him with studies on heredity, with the natural origin of human races, and with the idea that forms of life may have changed with time.

Joseph Gottlieb Kölreuter (1733–1806)

Source: Wikipedia

Joseph Gottlieb Kölreuter, also spelled Koelreuter or Kohlreuter, was a German botanist who pioneered the study of plant fertilization, hybridization and was the first to detect self-incompatibility. He was an observer as well as a rigorous experimenter who used careful crossing experiments although he did not inquire into the nature of heritability. Kölreuter was the oldest of three sons of an apothecary in Karlsruhe, Germany, and grew up in Sulz. He took an early interest in natural history and made a collection of local insects. At the age of fifteen he went to study medicine at the University of Tübingen under physician and botanist Johann Georg Gmelin who had returned from St. Petersburg. Gmelin had an interest in floral biology and he reprinted a work by Rudolf Jakob Camerarius (who also taught at Tübingen) who was the first to demonstrate sexual reproduction in plants. In his inaugural address in 1749 Gmelin talked the need for research on the origin of new species by hybridization. Kölreuter major works were produced as four reports Vorlaufige Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen (1761), Fortsetzung (1763), Zweyte Fortsetzung (1764), and Dritte Fortsetzung (1766). In all he conducted nearly 500 different hybridization experiments across 138 species and examined the pollen characteristics of over a 1000 plant species.

See Also:

Ernst Mayr. 1986. Joseph Gottlieb Kölreuter's Contributions to Biology. Osiris, 2:135-176.

Thomas Robert Malthus (1766–1834)

Source: Wikipedia

Thomas Robert Malthus was an English cleric and scholar, influential in the fields of political economy and demography. Malthus himself used only his middle name, Robert. In his book An Essay on the Principle of Population, Malthus observed that an increase in a nation's food production improved the well-being of the populace, but the improvement was temporary because it led to population growth, which in turn restored the original per capita production level. In other words, mankind had a propensity to utilize abundance for population growth rather than for maintaining a high standard of living, a view that has become known as the "Malthusian trap" or the "Malthusian spectre". Populations had a tendency to grow until the lower class suffered hardship and want and greater susceptibility to famine and disease, a view that is sometimes referred to as a Malthusian catastrophe. Malthus wrote in opposition to the popular view in 18th-century Europe that saw society as improving and in principle as perfectible. He saw population growth as being inevitable whenever conditions improved, thereby precluding real progress towards a utopian society: "The power of population is indefinitely greater than the power in the earth to produce subsistence for man". His views became influential, and controversial, across economic, political, social and scientific thought. Pioneers of evolutionary biology read him, notably Charles Darwin and Alfred Russel Wallace.

Thomas Andrew Knight (1759–1838)

Source: Wikipedia

Thomas Andrew Knight was a horticulturalist and botanist. He served as the 2nd President of the Royal Horticultural Society (1811-1838). He attended Balliol College, Oxford. After graduation, he took up the study of horticulture. Attention was first called to his work in 1795 by the publication of the results of his research into the propagation of fruit trees and the diseases prevalent among them. He used 10,000 acres (4,000 ha) of land he inherited to conduct breeding of plants including strawberries, cabbages and peas and built an extensive greenhouse. In 1797 he published his Treatise on the Culture of the Apple and Pear, and on the Manufacture of Cider and Perry, a work which passed through several editions. He was one of the leading students of horticulture in the eighteenth and nineteenth centuries, but his personal papers disappeared after his death. Knight performed basic physiological experiments on plants, which work had been performed before only rarely. He elucidated the effects of gravity on seedlings and how decay in fruit trees was passed on by grafting. In many respects his work looked back to that of Rev. Stephen Hales. His goals were always strictly practical, aiming to improve useful food plants by breeding for better qualities. The Downton strawberry was the ancestor of most important modern strawberries until recent times.

It is not widely known that Knight studied variation in peas and found many of the same results as Mendel, but he failed to make the same imaginative leap about how these changes took place. In 1799 he wrote:

But, as I foresaw that several years must elapse, before the success or failure of this process [note: "this process" refers to Knight's goal of producing improved varieties of apples] could possibly be ascertained, I wished, in the interval, to see what would be its effects on annual plants. Amongst these, none appeared so well calculated to answer my purpose as the common pea; not only because I could obtain many varieties of this plant, of different forms, sizes, and colours; but also, because the structure of its blossom, by preventing the ingress of insects and adventitious farina, has rendeed its varieties remarkably permanent. Thomas Andrew Knight. 1799. An Account of Some Experiments on the Fecundation of Vegetables. Philosophical Transactions of the Royal Society of London, 89:195-204.

Knight intentionally shut himself off from outside scientific influences. He refused to read anyone else's scientific papers until Sir Joseph Banks, with whom he had a voluminous correspondence, persuaded him to do so. Knight reported on all his work in the Transactions of the Royal Society of London.

See Also:

Conway Zirkle. 1951. Gregor Mendel & His Precursors. ISIS, 42:97-104.

Charles A Shull and J. Fisher Stanfield. Thomas Andrew Knight, In memoriam. Plant Phyisiology, 14:1-8.

Thomas Andrew Knight. 1799. An Account of Some Experiments on the Fecundation of Vegetables. Philosophical Transactions of the Royal Society of London, 89:195-204.

Jean-Baptiste Lamarck (1744–1829)

Source: Wikipedia

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, often known simply as Lamarck, was a French naturalist. He was a soldier, biologist, academic, and an early proponent of the idea that biological evolution occurred and proceeded in accordance with natural laws. In 1801, he published Système des animaux sans vertèbres, a major work on the classification of invertebrates, a term he coined. In an 1802 publication he became one of the first to use the term biology in its modern sense. Lamarck continued his work as a premier authority on invertebrate zoology. He is remembered, at least in malacology, as a taxonomist of considerable stature. The modern era generally remembers Lamarck for a theory of inheritance of acquired characteristics, called soft inheritance, Lamarckism or use/disuse theory, which he described in his 1809 Philosophie Zoologique. However, his idea of soft inheritance was, perhaps, a reflection of the wisdom of the time accepted by many natural historians. Lamarck's contribution to evolutionary theory consisted of the first truly cohesive theory of biological evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through use and disuse of characteristics, differentiating them from other organisms. Scientists have debated whether advances in the field of transgenerational epigenetics mean that Lamarck was to an extent correct, or not.

Carl Friedrich von Gärtner (1772–1850)

Source: Wikipedia

Carl Friedrich von Gärtner (or Karl Friedrich von Gaertner) was a well-known German botanist, and the son of Joseph Gaertner. He was a pioneer in the study of hybrids, and he is considered an important influence for Gregor Mendel. Gärtner, who was a protestant, challenged the doctrine of Carl Linnaeus of the "new special creation" which stated that new species of vegetation could arise through hybridization. He defended the stability of species, and argued that although the transmutation of species was evidently possible, the new species would not last because of a law of reversion which prevented them from spreading freely.

In Experiments on Plant Hybridization, Mendel wrote:

Gärtner by the results of [his] transformation experiments, was led to oppose the opinion of those naturalists who dispute the stability of plant species and believe in a continuous evolution of vegetation. He perceives in the complete transformation of one species into another an indubitable proof that species are fixed within limits beyond which they cannot change. Although this opinion cannot be unconditionally accepted we find on the other hand in Gärtner’s experiments a noteworthy confirmation of that supposition regarding variability of cultivated plants which has already been expressed.

Matthias Jakob Schleiden (1804–1881)

Source: Wikipedia

Matthias Jakob Schleiden was a German botanist and co-founder of cell theory, along with Theodor Schwann and Rudolf Virchow. Born in Hamburg, Schleiden was educated at University of Jena, then practiced law in Heidelberg, but soon developed his love for botany into a full-time pursuit. Schleiden preferred to study plant structure under the microscope. While a professor of botany at the University of Jena, he wrote Contributions to our knowledge of phytogenesis (1838), in which he stated that all parts of the plant organism are composed of cells. Thus, Schleiden and Schwann became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, discovered in 1831 by the Scottish botanist Robert Brown, and sensed its connection with cell division. Schleiden was one of the first German biologists to accept Charles Darwin's theory of evolution. He became professor of botany at the University of Dorpat in 1863. He concluded that all plant parts are made of cells and that an embryonic plant organism arises from the one cell.

Theodor Schwann (1810–1882)

Source: Wikipedia

Theodor Schwann was a German physiologist. His many contributions to biology include the development of cell theory, the discovery of Schwann cells in the peripheral nervous system, the discovery and study of pepsin, the discovery of the organic nature of yeast, and the invention of the term metabolism. In 1837, Matthias Jakob Schleiden viewed and stated that new plant cells formed from the nuclei of old plant cells. While dining that year with Schwann, the conversation turned on the nuclei of plant and animal cells. Schwann remembered seeing similar structures in the cells of the notochord (as had been shown by Müller) and instantly realized the importance of connecting the two phenomena. The resemblance was confirmed without delay by both observers, and the results soon appeared in Schwann's famous Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants, in which he declared that "All living things are composed of cells and cell products". This became cell theory or cell doctrine. In the course of his verification of cell theory, Schwann proved the cellular origin and development of the most highly differentiated tissues including nails, feathers, and tooth enamel. Schwann established a basic principle of embryology by observing that the ovum is a single cell that eventually develops into a complete organism.

Rudolf Virchow (1821–1902)

Source: Wikipedia

Rudolf Ludwig Carl Virchow was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician, known for his advancement of public health. He is known as "the father of modern pathology" because his work helped to discredit humourism, bringing more science to medicine. He is also known as the founder of social medicine and veterinary pathology, and to his colleagues, the "Pope of medicine". A prolific writer, his scientific writings alone exceeded 2,000 in number. Among his books, Cellular Pathology published in 1858 is regarded as the root of modern pathology. This work also popularised the third dictum in cell theory: Omnis cellula e cellula ("All cells come from cells"); although his idea originated in 1855. Virchow is credited with several very important discoveries. His most widely known scientific contribution is his cell theory, which built on the work of Theodor Schwann. He was one of the first to accept the work of Robert Remak, who showed the origins of cells was the division of pre-existing cells. He did not initially accept the evidence for cell division, believing it only occurs in certain types of cells. When it dawned on him that Remak might be right, in 1855, he published Remak's work as his own, which caused a falling out between the two. This work, Virchow encapsulated in the epigram Omnis cellula e cellula ("all cells (come) from cells"), which he published in 1855. He was an ardent anti-evolutionist. He referred to Charles Darwin as an "ignoramus" and his own student Ernst Haeckel, the leading advocate of Darwinism in Germany, as a "fool". He discredited the original specimen of Neanderthal man as nothing but that of a deformed human, and not an ancestral species.

Charles Darwin (1809–1882)

Source: Wikipedia

Charles Robert Darwin was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution. He established that all species of life have descended over time from common ancestors and, in a joint publication with Alfred Russel Wallace, introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. Darwin published his theory of evolution with compelling evidence in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species. By the 1870s, the scientific community and much of the general public had accepted evolution as a fact. However, many favoured competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed in which natural selection was the basic mechanism of evolution. In modified form, Darwin's scientific discovery is the unifying theory of the life sciences, explaining the diversity of life.

See Also:

Darwin Online: The world's largest and most widely used resource on Darwin, containing his complete publications, his private papers and manuscripts, and much supplementary material.

Alfred Russel Wallace (1823–1913)

Source: Wikipedia

Alfred Russel Wallace was a British naturalist, explorer, geographer, anthropologist, and biologist. He is best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858. This prompted Darwin to publish his own ideas in On the Origin of Species. Wallace did extensive fieldwork, first in the Amazon River basin and then in the Malay Archipelago, where he identified the faunal divide now termed the Wallace Line, which separates the Indonesian archipelago into two distinct parts: a western portion in which the animals are largely of Asian origin, and an eastern portion where the fauna reflect Australasia. He was considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography". Wallace was one of the leading evolutionary thinkers of the 19th century and made many other contributions to the development of evolutionary theory besides being co-discoverer of natural selection. These included the concept of warning colouration in animals, and the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridisation. Wallace was strongly attracted to unconventional ideas (such as evolution). His advocacy of spiritualism and his belief in a non-material origin for the higher mental faculties of humans strained his relationship with some members of the scientific establishment.

See Also:

The Alfred Russel Wallace Website

Encyclopædia Britannica: Alfred Russel Wallace

The Alfred Russel Wallace Page

The New Yorker: Missing Link, Alfred Russel Wallace, Charles Darwin’s neglected double.

NOVA: Great Minds Think Alike, How Alfred Wallace Came to Share Darwin's Revolutionary Insight

Wallace Online (the first complete edition of the writings of Alfred Russel Wallace, including the first compilation of his specimens)

Alfred Russel Wallace, Darwin Correspondence Project

Thomas Huxley (1825–1895)

Source: Wikipedia

Thomas Henry Huxleywas an English biologist specialising in comparative anatomy. He is known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. Huxley's famous debate in 1860 with Samuel Wilberforce was a key moment in the wider acceptance of evolution and in his own career. Huxley had been planning to leave Oxford on the previous day, but, after an encounter with Robert Chambers, the author of Vestiges, he changed his mind and decided to join the debate. Wilberforce was coached by Richard Owen, against whom Huxley also debated about whether humans were closely related to apes.

Huxley was slow to accept some of Darwin's ideas, such as gradualism, and was undecided about natural selection, but despite this he was wholehearted in his public support of Darwin. Instrumental in developing scientific education in Britain, he fought against the more extreme versions of religious tradition. Huxley was certainly not slavish in his dealings with Darwin. As shown in every biography, they had quite different and rather complementary characters. Important also, Darwin was a field naturalist, but Huxley was an anatomist, so there was a difference in their experience of nature. Lastly, Darwin's views on science were different from Huxley's views. For Darwin, natural selection was the best way to explain evolution because it explained a huge range of natural history facts and observations: it solved problems. Huxley, on the other hand, was an empiricist who trusted what he could see, and some things are not easily seen. With this in mind, one can appreciate the debate between them, Darwin writing his letters, Huxley never going quite so far as to say he thought Darwin was right.

Huxley's reservations on natural selection were of the type "until selection and breeding can be seen to give rise to varieties which are infertile with each other, natural selection cannot be proved". Huxley's position on selection was agnostic; yet he gave no credence to any other theory. Huxley was for about thirty years evolution's most effective advocate, and for some Huxley was "the premier advocate of science in the nineteenth century [for] the whole English-speaking world". [Lyons, Sherrie L (1999), Thomas Henry Huxley: the evolution of a scientist, New York.]

Gregor Mendel (1822–1884)

Source: Wikipedia

Gregor Johann Mendel was a scientist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire (today's Czech Republic) and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance.

See Also:

Vítězslav Orel. 1996. Gregor Mendel: The First Geneticist. Oxford: Oxford University Press. 376 pp.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — a facsimile of the original publication in German.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — translated into English.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — translated into English, with sidenote annotations.

Robin Marantz Henig. 2001. The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics. New York: Mariner Books. 304 pp.

Simon Mawer. 2006. Gregor Mendel: Planting the Seeds of Genetics. Harry N Abrams. 176pp.

Andrei, Amanda, ""Experiments in Plant Hybridization" (1866), by Johann Gregor Mendel". Embryo Project Encyclopedia (2013-09-04). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/6240.

Francis Galton (1822–1911)

Source: Wikipedia

Sir Francis Galton was an English Victorian statistician, progressive, polymath, sociologist, psychologist, anthropologist, eugenicist, tropical explorer, geographer, inventor, meteorologist, proto-geneticist, and psychometrician. He was knighted in 1909. Galton produced over 340 papers and books. He also created the statistical concept of correlation and widely promoted regression toward the mean. He was the first to apply statistical methods to the study of human differences and inheritance of intelligence, and introduced the use of questionnaires and surveys for collecting data on human communities, which he needed for genealogical and biographical works and for his anthropometric studies.

See Also:

GALTON.ORG — An extensive on-line collection, providing a biography, Galton's collected works, and more.

The Francis Galton Papers: A collection of digitized resources maintained by the Wellcome Library (part of the Wellcome Trust)

Ernst Haeckel (1834–1919)

Source: Wikipedia

Ernst Heinrich Philipp August Haeckel was a German biologist, naturalist, philosopher, physician, professor, marine biologist, and artist who discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms, and coined many terms in biology, including anthropogeny, ecology, phylum, phylogeny, stem cell, and Protista. Haeckel promoted and popularised Charles Darwin's work in Germany and developed the influential but no longer widely held recapitulation theory (ontogeny recapitulates phylogeny) claiming that an individual organism's biological development, or ontogeny, parallels and summarises its species' evolutionary development, or phylogeny. Haeckel studied under Karl Gegenbaur at the University of Jena for three years, earning a doctorate in zoology, before becoming a professor of comparative anatomy at the University of Jena, where he remained for 47 years, from 1862 to 1909. Between 1859 and 1866, Haeckel worked on many phyla such radiolarians, poriferans (sponges) and annelids (segmented worms). During a trip to the Mediterranean, Haeckel named nearly 150 new species of radiolarians. Haeckel was a zoologist, an accomplished artist and illustrator, and later a professor of comparative anatomy. He was one of the first to consider psychology as a branch of physiology. He also proposed the kingdom Protista in 1866. His chief interests lay in evolution and life development processes in general, including development of nonrandom form, which culminated in the beautifully illustrated Kunstformen der Natur (Art forms of nature). Darwin's 1859 book On the Origin of Species had immense popular influence, but although its sales exceeded its publisher's hopes it was a technical book rather than a work of popular science: long, difficult and with few illustrations. One of Haeckel's books did a great deal to explain his version of "Darwinism" to the world. It was a bestselling, provocatively illustrated book in German, titled Natürliche Schöpfungsgeschichte, published in Berlin in 1868, and translated into English as The History of Creation in 1876. It was frequently reprinted until 1926.

See Also:

The Tragic Sense of Life: Ernst Haeckel and the Struggle over Evolutionary Thought — an excellent biography of Haeckel.

Carl Nägeli (1817–1891)

Source: Wikipedia

Carl Wilhelm von Nägeli was a Swiss botanist. He studied cell division and pollination but became known as the man who discouraged Gregor Mendel from further work on genetics. He rejected natural selection as a mechanism of evolution, favouring orthogenesis driven by a supposed "inner perfecting principle". The writer Simon Mawer, in his book Gregor Mendel: Planting the Seeds of Genetics (2006), gives us an interesting and detailed account of Nägeli's correspondence with Mendel. Mawer underlines that, at the time Nägeli was writing to the friar from Moravia, Nägeli "must have been preparing his great work entitled A mechanico-physiological theory of organic evolution (published in 1884, the year of Mendel's death) in which he proposes the concept of the 'idioplasm' as the hypothetical transmitter of inherited characters". Mawer notes that, in this Nägeli book, there is not a single mention of the work of Gregor Mendel. That prompted him to write: "We can forgive von Nägeli for being obtuse and supercilious. We can forgive him for being ignorant, a scientist of his time who did not really have the equipment to understand the significance of what Mendel had done despite the fact that he (von Nägeli) speculated extensively about inheritance. But omitting an account of Mendel's work from his book is, perhaps, unforgivable." (Mawer 2006, p. 81)

Friedrich Miescher (1844–1895)

Source: Wikipedia

Johannes Friedrich Miescher was a Swiss physician and biologist. He was the first researcher to isolate nucleic acid. Miescher isolated various phosphate-rich chemicals, which he called nuclein (now nucleic acids), from the nuclei of white blood cells in 1869 in Felix Hoppe-Seyler's laboratory at the University of Tübingen, Germany, paving the way for the identification of DNA as the carrier of inheritance. The significance of the discovery, first published in 1871, was not at first apparent, and it was Albrecht Kossel who made the initial inquiries into its chemical structure. Later, Friedrich Miescher raised the idea that the nucleic acids could be involved in heredity.

See Also:

Ralf Dahm. 2008. Discovering DNA: Friedrich Miescher and the early years of nucleic acid research. Human Genetics, 122:565. doi:10.1007/s00439-007-0433-0

William Keith Brooks (1848–1908)

Source: Wikipedia

William Keith Brooks received a Bachelor of Arts degree from Williams College in 1870 and a PhD from Harvard in 1875. With the opening of The Johns Hopkins University in 1876, Brooks received one of the university's initial fellowships and he quickly advanced within the organization, ultimately serving as Professor of Zoology and Head of the Biological Department. At the young age of 36 he was elected a member of the National Academy. He was chosen as a member of the American Philosophical Society in 1886 and of the Academy of Natural Science in 1887. Although many of Brooks' scientific contributions represent solid, nineteeth-century work, his most lasting effect came from his long-standing conviction that the processes of heredity were themselves a proper subject of investigation. In 1876 he wrote a paper entitled "A Provisional Hypothesis of Pangenesis" and he gave the subject a book-length treatment in his The Law of Heredity. A Study of the Cause of Variation and the Origin of Living Organisms. He was known as both a man of deep, abstract thought and an excellent teacher, as evidenced by the fact that many of the still well-known pioneers of genetics had, at one time or another, studied with him: viz. Thomas Morgan, E. B. Wilson, and William Bateson.

Walther Flemming (1843–1905)

Source: Wikipedia

Walther Flemming was a German biologist and a founder of cytogenetics. Flemming trained in medicine at University of Rostock, graduating in 1868. Afterwards, he served in 1870–71 as a military physician in the Franco-Prussian War. From 1873 to 1876 he worked as a teacher at the University of Prague. In 1876 he accepted a post as a professor of anatomy at the University of Kiel. He became the director of the Anatomical Institute and stayed there until his death. With the use of aniline dyes he was able to find a structure which strongly absorbed basophilic dyes, which he named chromatin. He identified that chromatin was correlated to threadlike structures in the cell nucleus – the chromosomes (meaning coloured bodies), which were named thus later by German anatomist Wilhelm von Waldeyer-Hartz (1841–1923). The Belgian scientist Edouard Van Beneden (1846–1910) had also independently observed chromosomes. Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread. However, he did not see the splitting into identical halves, the daughter chromatids. He studied mitosis both in vivo and in stained preparations, using as the source of biological material the fins and gills of salamanders. These results were published first in 1878 and in 1882 in the seminal book Zellsubstanz, Kern und Zelltheilung (Cell substance, nucleus and cell division). On the basis of his discoveries, Flemming surmised for the first time that all cell nuclei came from another predecessor nucleus (he coined the phrase omnis nucleus e nucleo, after Virchow's omnis cellula e cellula).

See Also:

Neidhard Paweletz. 2001. Walther Flemming: pioneer of mitosis research. Nature Reviews Molecular Cell Biology, 2:72-75. | doi:10.1038/35048077

Eduard Strasburger (1844–1912)

Source: Wikipedia

Eduard Adolf Strasburger was a Polish-German professor who was one of the most famous botanists of the 19th century. Strasburger studied biological sciences in Paris, Bonn and Jena, receiving a PhD in 1866 after working with Nathanael Pringsheim. In 1868 he taught at the University of Warsaw. In 1869 he was appointed professor of botany at the University of Jena. Since 1881 he was head of the Botanisches Institut at the University of Bonn. Together with Walther Flemming, and Edouard van Beneden he elucidated chromosome distribution during cell division.

Édouard van Beneden (1846–1910)

Source: Wikipedia

Édouard Joseph Louis Marie Van Beneden was a Belgian embryologist, cytologist and marine biologist. He was professor of zoology at the University of Liège. He contributed to cytogenetics by his works on the roundworm Ascaris. In this work he discovered and described the process of meiosis — a two-cell-division process by which cells reduce the number of chromosomes in preparation for the production of gametes. Van Beneden also elucidated, together with Walther Flemming and Eduard Strasburger, the essential facts of mitosis — the single-cell-division process that distributes equal chromosome complements to each of the two daughter cells.

Wilhelm von Waldeyer (1836–1921)

Source: Wikipedia

Heinrich Wilhelm Gottfried von Waldeyer-Hartz was a German anatomist, famous for consolidating the neuron theory of organization of the nervous system and for naming the chromosome. He is also remembered in two macroanatomical structures of the human body which were named after him: Waldeyer's tonsillar ring (the lymphoid tissue ring of the naso- and oropharynx) and Waldeyer's glands (of the eyelids). Waldeyer also studied the basophilic stained filaments which had been found (by his colleague of Kiel, Walther Flemming) to be the main constituents of chromatin, the material inside the cell nucleus. Although the full significance of chromosomes for genetics and for cell biology was still to be discovered, these filaments were known to be involved in the phenomenon of cell division discovered by Flemming, named mitosis, as well as in meiosis. In 1888, Waldeyer coined the term chromosome — colored body — to describe them.

See Also:

T. Cremer and C. Cremer. 1988. Centennial of Wilhelm Waldeyer’s introduction of the term “chromosome” in 1888. Cytogenetics and Cell Genetics, 48:66–67. (DOI:10.1159/000132591)

Waldeyer's 1888 paper in which he uses the word chromosome: Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen.

Hans Driesch (1867–1941)

Source: Wikipedia

Hans Adolf Eduard Driesch was a German biologist and philosopher from Bad Kreuznach. He is most noted for his early experimental work in embryology and for his neo-vitalist philosophy of entelechy. He is also credited with performing the first 'cloning' of an animal in the 1880s. Driesch was educated at the Gelehrtenschule des Johanneums. He began to study medicine in 1886 under August Weismann at the University of Freiburg. In 1887 he attended the University of Jena under Ernst Haeckel, Oscar Hertwig and Christian Ernst Stahl. In 1888 he studied physics and chemistry at the University of Munich. He received his doctorate in 1889. He travelled widely on field and study trips and lecture-tours, visiting Plymouth, India, Zurich and Leipzig where, in 1894, he published his Analytische Theorie der organischen Entwicklung or Analytic Theory of Organic Development. By 1885 Driesch's experiments on the sea urchin embryo suggested that it was possible to remove large pieces from eggs, shuffle the blastomeres and interfere in many ways without affecting the resulting embryo. It appeared that any single monad in the original egg cell was capable of forming any part of the completed embryo. This important refutation of both preformation and the mosaic theory of Wilhelm Roux was to be subject to much discussion in the ensuing years, and caused friction among Driesch, Roux and Haeckel. In his work on sea urchins, dividing cells of the embryo after the first cell-division, he expected each cell to develop into the corresponding half of the animal to which it has been destined or preprogrammed, but instead found that each developed into a complete sea urchin. This also happened at the four-cell stage: entire larvae ensued from each of the four cells, albeit smaller than usual. Driesch's findings brought about the adoption of the terms "totipotent" and "pluripotent" cell, referring respectively to a cell that can generate every cell in an organism and one that can generate nearly every cell. Driesch's results were confirmed with greater precision by Hans Spemann.

Oscar Hertwig (1849–1922)

Source: Wikipedia

Oscar Hertwig was a German zoologist and professor, who also wrote about the theory of evolution circa 1916, over 55 years after Charles Darwin's book The Origin of Species. Oscar Hertwig was a leader in the field of comparative and causal animal-developmental history. He also wrote a leading textbook. By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell. He recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he published his findings that fertilization includes the penetration of a spermatozoon into an egg cell. Oscar Hertwig experiments with frog eggs revealed the 'long axis rule', or Hertwig rule. According to this rule cell divides along its long axis (1884). While Oscar was well interested in developmental biology, he was opposed to chance as assumed in Charles Darwin´s theory. His most important theoretical book was: Das Werden der Organismen, eine Widerlegung der Darwinschen Zufallslehre (Jena, 1916) (translation: The Origin of Organisms – a Refutation of Darwin's Theory of Chance).

See Also:

Brind'Amour, Katherine,, Garcia, Benjamin, "Wilhelm August Oscar Hertwig (1849-1922)". Embryo Project Encyclopedia (2007-11-01). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1707.

Churchill, F B (1970), "Hertwig, Weismann, and the meaning of reduction division circa 1890.", Isis; an international review devoted to the history of science and its cultural influences, 61:429–57.

August Weismann (1834–1914)

Source: Wikipedia

August Friedrich Leopold Weismann was a German evolutionary biologist. Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg. His main contribution involved his Germ Plasm Theory, at one time also known as Weismannism, according to which inheritance (in a multicellular organism) only takes place by means of the germ cells — the gametes such as egg cells and sperm cells. Other cells of the body — somatic cells — do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. The idea of the Weismann barrier is central to the modern evolutionary synthesis, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection. Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time".

See Also:

Essays Upon Heredity — a collection of Weismann's writing on hereditary issues.

Yawen Zou. 2015. The Germ-Plasm: a Theory of Heredity (1893), by August Weismann. The Embryo Project Encyclopedia.

Edwin G. Conklin. 1915. August Weismann. Proceedings of the American Philosophical Society, 54:3-12.

Edmund Beecher Wilson (1856–1939)

Source: Wikipedia

Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell in Development and Inheritance. He and Nettie Maria Stevens were the first researchers to describe the chromosomal basis of sex, but they conducted their research independently of each other. Wilson is credited as America's first cell biologist. In 1898 he used the similarity in embryos to describe phylogenetic relationships. By observing spiral cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells and concluded that all these organisms must have a common ancestor.

William Bateson (1861–1926)

Source: Wikipedia

William Bateson was an English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscovery in 1900 by Hugo de Vries and Carl Correns. Bateson first suggested using the word "genetics" to describe the study of inheritance and the science of variation in a personal letter to Adam Sedgwick who had been Darwin's professor), dated 18 April 1905. Bateson first used the term "genetics" publicly at the Third International Conference on Plant Hybridization in London in 1906.

Erich von Tschermak (1864–1933)

Source: Wikipedia

Erich Tschermak, Edler von Seysenegg was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gustav Tschermak von Seysenegg. His maternal grandfather was the famous botanist, Eduard Fenzl, who taught Gregor Mendel botany during his student days in Vienna.

Carl Correns (1864–1933)

Source: Wikipedia

Carl Erich Correns was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, and for his rediscovery of Gregor Mendel's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich Tschermak von Seysenegg and Hugo de Vries, and the agronomist William Jasper Spillman. Carl Correns conducted much of the foundational work for the field of genetics at the turn of the 20th century. He rediscovered and independently verified the work of Mendel in a separate model organism. He also discovered cytoplasmic inheritance, an important extension of Mendel's theories, which demonstrated the existence of extra-chromosomal factors on phenotype. Most of Correns' work went unpublished however, and was destroyed in the Berlin bombings of 1945.

Hugo de Vries (1848–1935)

Source: Wikipedia

Hugo Marie de Vries was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution. In 1889, De Vries published his book Intracellular Pangenesis, in which, based on a modified version of Charles Darwin's theory of Pangenesis of 1868, he postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles. He called these units pangenes, a term 20 years later to be shortened to genes by Wilhelm Johannsen.

See Also:

Ralph E. Cleland. 1936. Hugo de Vries. Proceedings of the American Philosophical Society, 76:248-250.

Theodor Boveri (1862–1915)

Source: Embryo Project

Theodor Heinrich Boveri was a German biologist. He was notable for first hypothesising the cellular processes that cause cancer. Boveri's work with sea urchins showed that it was necessary to have all chromosomes present in order for proper embryonic development to take place. This discovery was an important part of the Boveri–Sutton chromosome theory, which identifies chromosomes as the carriers of genetic material. The theory correctly explains the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors (particles) required by Mendel's laws. The chromosome theory of inheritance is credited to papers by Walter Sutton in 1902 and 1903, as well as to independent work by Theodor Boveri during roughly the same period. Boveri's thoughts are summarized in his book Ergebnisse über die Konstitution der chromatischen Substanz des Zellkerns (Results on the constitution of the chromatic substance of the cell nucleus), Jena: Verlag von Gustav Fischer, 1904. His other significant discovery was the centrosome (1888), which he described as the especial organ of cell division. Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode Parascaris.

Archibald Garrod (1857–1938)

Source: Wikipedia

Sir Archibald Edward Garrod was an English physician who pioneered the field of inborn errors of metabolism. He also discovered alkaptonuria, understanding its inheritance. He served as Regius Professor of Medicine at the University of Oxford from 1920 to 1927. Garrod is best known for his scientific study of inborn errors of metabolism. He developed an increasing interest in chemical pathology, and investigated urine chemistry as a reflection of systemic metabolism and disease. This research, combined with the new understanding of Mendelian inheritance, evolved from an investigation of a few families with an obscure and not very dangerous disease (alkaptonuria) to the realization that a whole territory of mysterious diseases might be understood as inherited disorders of metabolism. Working with William Bateson, Garrod came to understand the pattern of alkaptonuria appearance in children based on Mendelian principles. Once he applied Mendel’s concepts to alkaptonuria, he published a paper in 1902 called The Incidence of Alkaptonuria: A Study of Chemical Individuality. In the paper, Garrod explains how he came to understand the condition and speculates as to its causes. He cites various case studies and compares alkaptonuria to albinism in how it is inherited. He summarized his thoughts on the relationship of inheritance to metabolic disease in his book Inborn Errors of Metabolism .

See Also:

F. G. Hopkins. 1938. Archibald Edward Garrod. 1857–1936. Biographical Memoirs of fellows of the Royal Society, 2:225–228.

Krishna Dronamraju. 1992. BIOGRAPHY Profiles in Genetics: Archibald E. Garrod (1857-1936). american Journal of Human Genetics, 51:216-219.

Raphael Weldon (1860–1906)

Source: Wikipedia

Walter Frank Raphael Weldon, generally called Raphael Weldon, was an English evolutionary biologist and a founder of biometry. He was the joint founding editor of Biometrika, with Francis Galton and Karl Pearson. Medicine was his intended career and he spent the academic year 1876-1877 at University College London. Among his teachers were the zoologist E. Ray Lankester and the mathematician Olaus Henrici. In the following year he transferred to King's College London and then to St John's College, Cambridge in 1878. There Weldon studied with the developmental morphologist Francis Balfour who influenced him greatly; Weldon gave up his plans for a career in medicine. In 1881 he gained a first-class honours degree in the Natural Science Tripos; in the autumn he left for the Naples Zoological Station to begin the first of his studies on marine biological organisms.

Upon returning to Cambridge in 1882, he was appointed university lecturer in Invertebrate Morphology. Weldon's work was centred on the development of a fuller understanding of marine biological phenomena and selective death rates of these organisms. In 1889 Weldon succeeded Lankester in the Jodrell Chair of Zoology at University College London, and was elected to the Royal Society in 1890. Royal Society records show his election supporters included the great zoologists of the day: Huxley, Lankester, Poulton, Newton, Flower, Romanes and others. His interests were changing from morphology to problems in variation and organic correlation. He began using the statistical techniques that Francis Galton had developed for he had come to the view that "the problem of animal evolution is essentially a statistical problem." Weldon began working with his University College colleague, the mathematician Karl Pearson. Their partnership was very important to both men and survived Weldon's move to the Linacre Chair of Zoology at Oxford University in 1899. In the years of their collaboration Pearson laid the foundations of modern statistics.

In 1900 the work of Gregor Mendel was rediscovered and this precipitated a conflict between Weldon and Pearson on the one side and William Bateson on the other. Bateson, who had been taught by Weldon, took a very strong line against the biometricians. This bitter dispute ranged across substantive issues of the nature of evolution and methodological issues such as the value of the statistical method. In The Origins of Theoretical Population Genetics, William Provine gives a detailed account of the controversy. The debate lost much of its intensity with the death of Weldon in 1906, though the general debate between the biometricians and the Mendelians continued until the creation of the modern evolutionary synthesis in the 1930s.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Online Weldon Biography

Weldon, Walter Frank Raphael. Encyclopedia of Mathematics

P Froggatt and N C Nevin. 1971. The 'law of ancestral heredity' and the Mendelian-ancestrian controversy in England, 1889-1906. Journal of Medical Genetics, 8:1-36.

Weldon, W. F. R. 1902. Mendel's laws of alternative inheritance in peas. Biometrika, 1:228-254.

Karl Pearson. 1906. "Walter Frank Raphael Weldon 1860-1906," Biometrika, 5:1-52.

Clarence Erwin McClung (1870–1946)

Source: Wikipedia

Clarence Erwin (CE) McClung was an American zoologist of wide-ranging interests. Although born in California, he spent much of his early life in Kansas. He originally studied pharmacy at Kansas University, receiving the Ph.G. degree in 1892. He taught pharmacy at the University for a year, but then his interest shifted to more general biological questions and he reenrolled as a student. From Kansas University he received the A.B. degree in 1896, the A.M. in 1898, and the Ph.D. in 1902. CE McClung made important contributions to early genetics, but he was also a general zoologist and paleontologist who received all of his degrees from Kansas and then spent his early career on the faculty there, ultimately assuming the positions of chair of the zoology department, curator of vertebrate paleontology, and even acting dean of the medical school. Early in his career, he undertook an investigation of spermatogenesis in Ziphidium fasciatum, a long-horned grasshopper. In this material he recognized that an object thought by some to be a nucleolus was actually an unpaired chromosome. Although others had noticed that this object was distributed asymmetrically into some but not all spermatozoa, McClung was the first to see that this could provide a cytological mechanism of sex determination.

See Also:

D. H. Wenrich. 1946. Clarence Erwin McClung 1870-1946 Science, 103:551-552. DOI: 10.1126/science.103.2679.551

David Henry Wenrich Papers: A collection largely developed to support the Dr. Wenrich's efforts to honor Dr. Clarence Erwin McClung.

Walter S. Sutton (1877–1916)

Source: The Electronic Scholarly Publishing Project

Walter Stanborough Sutton was an American geneticist and physician whose most significant contribution to present-day biology was his theory that the Mendelian laws of inheritance could be applied to chromosomes at the cellular level of living organisms. This is now known as the Boveri-Sutton chromosome theory.

After graduating high school in Russell, he enrolled at the University of Kansas in engineering in 1896. Following the death of his younger brother (John) from typhus in 1897, Sutton switched his major to biology with an interest in medicine. While at the University of Kansas, both he and his older brother, William Sutton, played basketball for Dr. James Naismith. Sutton distinguished himself as student being elected to both Phi Beta Kappa and Sigma Xi and receiving both bachelor's and master's degrees by 1901. For his Masters thesis, he studied the spermatogenesis of Brachystola magna, a large grasshopper indigenous to the farmlands upon which Sutton was raised.

Considering the advice of his mentor at KU, Dr. C. E. McClung, Sutton moved to Columbia University for further study of zoology under Dr. Edmund B. Wilson. It was here that Sutton wrote his two significant works in genetics – “On the morphology of the chromosome group in Brachystola magna” and “The chromosomes in heredity”. The German biologist Theodor Boveri independently reached the same conclusions as Sutton, and their concepts are often referred to as the Boveri-Sutton chromosome theory. Sutton’s hypothesis was widely accepted by most scientists, particularly cytologists, at the time. The continued work of Thomas Hunt Morgan at Columbia brought the theory to universal acceptance by 1915 through his studies of Drosophila melanogaster, the fruit fly, even as William Bateson continued to question the theory until 1921. Sutton did not complete his PhD in Zoology as he originally planned. At the age of 26, he returned to the Kansas oil fields for 2 years. There he was able to perfect a device to start large gas engines with high pressure-gas and develop hoisting apparatuses for deep wells. Sutton’s mechanical aptitudes never left him. His father finally directed him to return to his medical studies and he did so returning to Columbia University in 1905. Sutton’s medical studies proceeded through the College of Physicians and Surgeons at Columbia University. While he continued to work on patents associated with oil drilling, Sutton also began at this stage to apply his mechanical aptitude to improving medical instruments. With credit for his graduate studies at both the University of Kansas and Columbia University, Sutton obtained his doctorate in medicine in 1907 graduating with “high standing”. He then began an internship at Roosevelt Hospital in New York working in the surgical division headed by Dr. Joseph Blake.

In 1909, Sutton returned to Kansas City, Kansas where his family had relocated and his father and brother were in law practice. Sutton was appointed assistant professor of surgery at the four-year-old University of Kansas Medical School. The tenuous nature of the appointment at the young school led him to also maintain a private practice and serve on the staff of St. Margaret’s Hospital as well as the University’s Bell Memorial Hospital. For six years, Sutton performed a wide range of surgeries carefully documenting the procedures. He published several articles related to these cases going back to his internship at Roosevelt. In 1911, he had accepted a commission as a First Lieutenant in the United States Army Medical reserve Corps. This eventually led to his taking a leave of absence from the University in February, 1915 to serve at the American Ambulance Hospital outside Paris. Sutton and others from his days at Columbia and Roosevelt arrived at College of Juilly on February 23 where hospital facilities had been set up only 40 miles from the front lines of World War I. Within 2 months, he was surgeon-in-chief handling administrative duties in addition to his surgical responsibilities. His inventive aptitude was perhaps never more valued as he developed fluoroscopic techniques to identify and localize shrapnel within the soldier’s bodies and then removed the foreign items with instruments of his own design. After his return, he documented these techniques in Binnie’s Manual of Operative Surgery.[11] Sutton’s return sailing from France was on June 26, 1915 having stayed only four months, but have made a significant contribution to wartime medical treatment. Dr. Sutton died rather unexpectedly at the age of 39 due to complications from acute appendicitis.

See Also:

Sutton, Walter S. 1902. On the morphology of the chromosome group in Brachystola magna. Biological Bulletin, 4:24-39.

Sutton, Walter S. 1903. The chromosomes in heredity. Biological Bulletin, 4: 231-251.

WIKIPEDIA: Walter Sutton

Crow, JF and Crow, EW 2002. 100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity. Genetics, 160:1-4.

The Embryo Project Encyclopedia: Walter Stansborough Sutton (1877–1916)

Hulston, Nancy Walter S. Sutton, MD: A Genius Goes To War

McKusick, Victor A. 1960. Walter S. Sutton and the Physical Basis of Mendelism. Bulletin of the History of Medicine, 34: 487.

Nettie Marie Stevens (1861–1912)

Source: Wikipedia

Nettie Maria Stevens was an early American geneticist. In 1906, she discovered that male beetles produce two kinds of sperm, one with a large chromosome and one with a small chromosome. When the sperm with the large chromosome fertilized eggs, they produced female offspring, and when the sperm with the small chromosome fertilized eggs, they produced male offspring. This pattern was observed in other animals, including humans, and became known as the XY sex-determination system.

See Also:

Smith, Kaitlin, "Nettie Maria Stevens (1861-1912)". Embryo Project Encyclopedia (2010-06-20). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/2028.

Reginald Crundall Punnett (1875–1967)

Source: Wikipedia

Reginald Crundall Punnett was a British geneticist who co-founded, with William Bateson, the Journal of Genetics in 1910. Punnett is probably best remembered today as the creator of the Punnett square, a tool still used by biologists to predict the probability of possible genotypes of offspring. His little book (62 small pages) Mendelism (1905) is sometimes said to have been the first textbook on genetics; it was probably the first popular science book to introduce genetics to the public.

Lucien Cuénot (1866–1951)

Source: Wikipedia

Lucien Claude Marie Julien Cuénot was a French biologist. In the first half of the 20th century, Mendelism was not a popular subject among French biologists. Cuénot defied popular opinion and shirked the “pseudo-sciences” as he called them. Upon the rediscovery of Mendel's work by Correns, De Vries, and Tschermak, Cuénot proved that Mendelism applied to animals as well as plants. Cuénot spent two years working on mice and came to the conclusion that three “mnemons” (genes) are responsible for the production of one “chromogen” or pigment and two “distases” enzymes. The pigment (if present) is acted upon by the enzymes to produce black or yellow colour. If no pigment is present the result is an albino mouse. Cuénot studied the offspring of various crosses between mice and concluded that these “mnemons” or genes were inherited in a Mendelian fashion. Subsequently, Cuénot was the first person to describe multiple allelism at a genetic locus. He also described a lethal mutation in the mouse agouti locus at a time when such a mutation was unheard of.

See Also:

Jean Gayon and Richard M. Burian. 2000. France in the Era of mendelism. Comptes rendus de l’Académie des Sciences, Paris. Sciences de la vie / Life Sciences, 323:1097-1106.

Godfrey Harold Hardy (1877–1947)

Source: Wikipedia

Godfrey Harold "G. H." Hardy was an English mathematician, known for his achievements in number theory and mathematical analysis. In addition to his research, Hardy is remembered for his 1940 essay on the aesthetics of mathematics, entitled A Mathematician's Apology. He was the mentor of the Indian mathematician Srinivasa Ramanujan.

Although every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and although nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics, most biologists don't realize that Hardy's total contribution to biology consisted of a single one-page letter to the editor in Science.

The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics. Mathematically, Hardy's "very simple point" was the trivial assertion that (p + q)² = p² + 2pq + q² Biologically, however, Hardy's point was of greater consequence, as his simple algebra implied that Mendelian mechanisms, acting alone, have no effect upon allele frequencies in a population — an observation that was far from obvious to most biologists.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Wilhelm Weinberg (1862–1937)

Source: Wikipedia

Dr Wilhelm Weinberg was a German obstetrician-gynecologist, practicing in Stuttgart, who in a 1908 paper, published in German in Jahresheft des Vereins für vaterländische Naturkunde in Württemberg (The Annals of the Society of National Natural History in Württemberg), expressed the concept that would later come to be known as the Hardy-Weinberg principle. Weinberg is also credited as the first to explain the effect of ascertainment bias on observations in genetics. Weinberg developed the principle of genetic equilibrium independently of British mathematician G.H. Hardy. He delivered an exposition of his ideas in a lecture on January 13, 1908, before the Verein für vaterländische Naturkunde in Württemberg (Society for the Natural History of the Fatherland in Württemberg), about six months before Hardy's paper was published in English. His lecture was printed later that year in the society's yearbook. Weinberg's contributions were unrecognized in the English speaking world for more than 35 years. Curt Stern, a German scientist who immigrated to the United States before World War II, pointed out in a brief paper in Science that Weinberg's exposition was both earlier and more comprehensive than Hardy's. Before 1943, the concepts in genetic equilibrium that are known today as the Hardy-Weinberg principle had been known as "Hardy's law" or "Hardy's formula" in English-language texts.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Calvin Blackman Bridges (1889–1938)

Source: Wikipedia

Calvin Blackman Bridges was born in Schuyler Falls, New York in 1889 to the parents of Leonard Bridges and Charlotte Blackman. Tragically, Calvin's mother died when he was two years old, and his father died a year after his mother's death, leaving Calvin Bridges an orphan. Following the death of his parents, Bridges was taken in and raised by his grandmother. Despite now being known in the scientific world as one of the most influential researchers regarding Drosophila melanogaster, it took Bridges several years to complete high school, graduating when he was 20 years old. However, despite this setback, Bridges moved on to be an outstanding student at Columbia University, which he attended both for undergraduate and postgraduate school. While taking a zoology class, Bridges met Thomas Hunt Morgan. This started a relationship which would lead to many important discoveries in the scientific world regarding genetics and evolution. Bridges wrote a masterful Ph.D. thesis on Non-disjunction as proof of the chromosome theory of heredity (click HERE for part 2 ) which appeared as the first paper in the first issue of the journal Genetics in 1916. In this paper, he also established that the Y-chromosome does not determine gender in Drosophila.

See Also:

Gleason, Kevin, "Calvin Blackman Bridges (1889-1938)". Embryo Project Encyclopedia (2017-05-19). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/11504.

Thomas Hunt Morgan (1866–1945)

Source: Wikipedia

Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Morgan received his Ph.D. from Johns Hopkins University in zoology in 1890 and researched embryology during his tenure at Bryn Mawr. Following the rediscovery of Mendelian inheritance in 1900, Morgan began to study the genetic characteristics of the fruit fly Drosophila melanogaster. In his famous Fly Room at Columbia University, Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of genetics. During his distinguished career, Morgan wrote 22 books and 370 scientific papers. As a result of his work, Drosophila became a major model organism in contemporary genetics. The Division of Biology which he established at the California Institute of Technology has produced seven Nobel Prize winners.

See Also:

Garland E. Allen. 1979. Thomas Hunt Morgan: The Man and His Science. Princeton: Princeton University Press. 447 pp. (The definitive biography)

Robert E. Kohler. 1994. Lords of the Fly: Drosophila Genetics and the Experimental Life. Chicago: University of Chicago Press. 344pp. (An excellent treatment of the early work in Drosophila genetics)

H. J. Muller. 1946. Thomas Hunt Morgan 1866–1945. Science, 103:550–551.

Diana E. Kenney and Gary G. Borisy. 2009. Thomas Hunt Morgan at the Marine Biological Laboratory: Naturalist and Experimentalist. Genetics, 181:841-846.

R. A. Fisher and G. R. de Beer. 1947. Thomas Hunt Morgan. 1866–1945. Obituary Notices of Fellows of the Royal Society, 5:451-466.

Stephen G. Brush. 2002. How Theories became Knowledge: Morgan's Chromosome Theory of Heredity in America and Britain. Journal of the History of Biology, 35:471–535.

Norman H. Horowitz. 1998. T. H. Morgan at Caltech: A Reminiscence. Genetics, 149:1629–1632.

Hermann Joseph Muller (1890–1967)

Source: Wikipedia

Hermann Joseph Muller (or H. J. Muller) was an American geneticist, educator, and Nobel laureate best known for his work on the physiological and genetic effects of radiation (Mutagenesis) as well as his outspoken political beliefs. Muller frequently warned of the long-term dangers of radioactive fallout from nuclear war and nuclear testing, helping to raise public awareness in this area. At 16 he entered Columbia College. From his first semester he was interested in biology; he became an early convert of the Mendelian-chromosome theory of heredity — and the concept of genetic mutations and natural selection as the basis for evolution. Muller remained at Columbia (the pre-eminent American zoology program at the time, thanks to E. B. Wilson and his students) for graduate school. He became interested in the Drosophila genetics work of Thomas Hunt Morgan's fly lab after undergraduate bottle washers Alfred Sturtevant and Calvin Bridges joined his Biology Club. He joined Morgan's group in 1912 (after two years of informal participation). In 1918, he proposed an explanation for the dramatic discontinuous alterations in Oenothera larmarckiana that were the basis of Hugo de Vries's theory of mutationism: "balanced lethals" allowed the accumulation of recessive mutations, and rare crossing over events resulted in the sudden expression of these hidden traits. In other words, de Vries's experiments were explainable by the Mendelian-chromosome theory.

Alfred Henry Sturtevant (1891–1970)

Source: Wikipedia

Alfred Henry Sturtevant was an American geneticist. While still a student, Sturtevant constructed the first genetic map of a chromosome in 1913. Throughout his career he worked on the organism Drosophila melanogaster with Thomas Hunt Morgan. By watching the development of flies in which the earliest cell division produced two different genomes, he measured the embryonic distance between organs in a unit which is called the sturt in his honor. In 1965, Sturtevant published a first-rate, first-person account of A History of Genetics.

See Also:

Edward B. Lewis. Alfred Henry Sturtevant November 21, 1891 – April 5, 1970. Biographical Memoirs of the National Academy of Science, 73:348–362.

Guide to the Alfred H. Sturtevant Papers, 1849-1969. Online Archive of California.

Thomas H. Montgomery, Jr. (1873–1912)

Source: Wikipedia

Thomas Harrison Montgomery Jr. was an American zoologist who made important contributions to cell biology–especially in chromosomes and their roles in sex determination–as well as the biology of birds and several groups invertebrates, naming many species of ribbon worms, rotifers, and spiders. He studied in Berlin before becoming a researcher and professor at the University of Pennsylvania, where he primarily worked until his death at the age of 39. In his short career he published 80 scientific papers and two books.

Harrison published 25 papers on cell biology, primarily using insect cells. His most notable research includes early observations of the pairing of maternal and paternal chromosomes during cell division. He was first to propose that chromosomes play the dominant role in sex determination, although he rejected the idea that sex was determined by chromosomes alone, and some historians claim he was the first to propose the chromosome theory of inheritance, an idea widely credited to Walter Sutton and Theodor Boveri. He also detailed the morphology of the nucleolus, and observed that in some hemipteran insects the germ cells of males but not females contain odd numbers of chromosomes, which is now known to influence sex-determination, A resolution of the American Society of Zoologists read after his death stated "it would be impossible to write a text-book upon the role of the chromosomes in the determination of sex without referring to his crucial labors in this field."

See Also:

Conklin, Edwin G. 1913. PROFESSOR THOMAS HARRISON MONTGOMERY, JR. Science, 38:207-214. DOI: 10.1126/science.38.972.207

Montgomery, Thos. H., Jr. 1910. ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS? Biological Bulletin, 19:1-17.

John Burton Sanderson Haldane (1892–1964)

Source: Wikipedia

John Burdon Sanderson Haldane was a British-born scientist known for his work in the study of physiology, genetics, evolutionary biology, and in mathematics, where he made innovative contributions to the fields of statistics and biostatistics. He was the son of the equally famous John Scott Haldane and was a professed socialist, Marxist, atheist, and humanist whose political dissent led him to leave England in 1956 and live in India, becoming a naturalised Indian citizen in 1961. His first paper in 1915 demonstrated genetic linkage in mammals while subsequent works helped to create population genetics, thus establishing a unification of Mendelian genetics and Darwinian evolution by natural selection whilst laying the groundwork for modern evolutionary synthesis.

He was one of the three major figures to develop the mathematical theory of population genetics, along with Ronald Fisher and Sewall Wright. Thusly he played an important role in the modern evolutionary synthesis, which is popularly called "neo-Darwinism", as in Richard Dawkins' 1976 work titled The Selfish Gene. He re-established natural selection as the premier mechanism of evolution by explaining it in terms of the mathematical consequences of Mendelian inheritance. He wrote a series of ten papers called A Mathematical Theory of Natural and Artificial Selection, on the numerical formalism underpinning natural selection. It showed that gene frequencies have direction and rates of change; and he pioneered the interaction of natural selection with mutation and animal migration. Haldane's book, The Causes of Evolution (1932), summarised these results, especially in its extensive appendix.

Arthur C. Clarke credited him as "perhaps the most brilliant science populariser of his generation". Nobel laureate Peter Medawar called Haldane "the cleverest man I ever knew".

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Frederick Twort (1877–1950)

Source: Wikipedia

Frederick William Twort was an English bacteriologist and was the original discoverer in 1915 of bacteriophages (viruses that infect bacteria). He studied medicine at St Thomas's Hospital, London, was superintendent of the Brown Institute for Animals (a pathology research centre), and was a professor of bacteriology at the University of London. He researched into Johne's disease, a chronic intestinal infection of cattle, and also discovered that vitamin K is needed by growing leprosy bacteria.

Early in the history of microbiology, bacteria were often differentiated testing their ability to grow on different media. Twort's first important paper found some shortcomings to this method. He found that the major subgroups identified by sugar fermentation were not capable of clear-cut subdivision by tests on glucosides, nor even were they strictly separable by sugars. Twort wrote, "It seems, therefore, probable that the separate micro-organisms in the various subgroups are not to be regarded as distinct species, but as varieties or hybrids of one or more species. If this be so, one might expect them to be constantly varying, losing old characters and gaining new ones according to the conditions under which they are grown, and it was with the object of testing this hypothesis that further series of experiments were undertaken." Following prolonged incubation in media that they previously failed to ferment, several species acquired fermentation powers which originally they did not enjoy. We now know that these mutant individuals able to ferment novel sugars arose in culture, and came to dominate the population. Although ignored at the time — a trend that seemed to plague his career — this work was quite prescient, and anticipated by decades the subsequent work on adaptation and mutation by bacterial chemists and microbiologists.

Twort and his brother, Dr. C. C. Twort, had for some years been trying to grow viruses in artificial media hoping to find a nonpathogenic virus, which might be the wild type of a pathogenic one, so more likely to grow. In 1914, Twort set out to identify the elusive (now known to be nonexistent) "essential substance" that would allow vaccinia virus to grow in vitro. At the time, smallpox vaccines had to be made in the skin of calves and was almost always contaminated with the bacterial genus Staphylococcus. Twort speculated the contaminating bacteria might be the source of the "essential substance" needed by vaccinia to survive. He plated some of the smallpox vaccines on nutrient agar slants and obtained large bacterial colonies of several colours. Upon closer examination of the colonies with a magnifying glass, he found minute glassy areas that would not grow when subcultured. He quickly realized these glassy areas were the result of the destruction of the bacterial cells and was able to pick from some of these areas and transmit this from one staphylococci colony to another.

Further experiments showed the agent could pass through porcelain filters and it required bacteria for growth. These observations show Twort had discovered most of the essential features of bacteriophages, although Twort seemed to favor the idea that the principle was not a separate form of life, but an enzyme which is secreted by the bacteria. Twort published these results in The Lancet in 1915 and called the contagion the bacteriolytic agent. Unfortunately, his discovery was ignored; Félix d'Herelle discovered phages independently, and Twort's work may have been lost to time, but for Jules Bordet and Andre Gratia's rediscovery of Twort's paper.

See Also:

Duckworth, D. H. 1976. "Who discovered bacteriophage?". Bacteriological Reviews. 40:793–802.

William E. Castle (1867–1962)

Source: Wikipedia

William Ernest Castle was born on a farm in Ohio and took an early interest in natural history. He graduated in 1889 from Denison University in Granville, Ohio, a Baptist college that emphasized classics, and went on to become a teacher of Latin at Ottawa University in Ottawa, Kansas, where he published his first paper on the flowering plants of the area. After three years of teaching, botany won out over Latin. Castle entered the senior class of Harvard University in 1892 and in 1893 took a second A.B. degree with honors. He was appointed laboratory assistant in zoology, an A.M. degree in 1894 and a Ph.D. in 1895. He then taught zoology at the University of Wisconsin–Madison and at the Knox College in Galesburg, Illinois, each for a year.

Castle returned to Harvard in 1897. His early work focused on embryology, but after the rediscovery of Mendelian genetics in 1900, he turned to mammalian genetics, especially that of the guinea pig. At Harvard, Charles W. Woodworth suggested to him that Drosophila might be used for genetical work. Castle was the first to use the fruit fly Drosophila melanogaster, and it was his work that inspired T. H. Morgan to use Drosophila and the basis of Morgan's 1933 Nobel Prize. In 1908 Castle moved from the Harvard Museum of Comparative Zoology to the Bussey Institution for Applied Biology. There his most famous PhD student was Sewall Wright who graduated in 1915. The same year he was elected to membership in the U.S. National Academy of Sciences. When the Eugenics Record Office was founded in 1912, he served as a member of its scientific advisory board, and in 1916 he was one of the 10 founders of the scientific journal Genetics.

See Also:

Dunn, L. C. 1965. William Ernest Castle 1867 – 1962. Biographical Memoirs, National Academy of Sciences.

Castle, W. E. 1911. Heredity in Relation to Evolution and Animal Breeding. New York: D. Appleton and Company. 184 pp.

William E. Castle Papers. American Philosophical Society.

Félix d'Herelle (1873–1949)

Source: Wikipedia

Félix d'Herelle was a French-Canadian microbiologist. He was co-discoverer of bacteriophages (viruses that infect bacteria) and experimented with the possibility of phage therapy. D'Herelle has also been credited for his contributions to the larger concept of applied microbiology.

In 1915, British bacteriologist Frederick W. Twort discovered a small agent that infects and kills bacteria, but did not pursue the issue further. Independently, the discovery of "an invisible, antagonistic microbe of the dysentery bacillus" by d'Herelle was announced on September 3, 1917. The isolation of phages by d'Herelle works like this: (1) Nutritional medium is infected with bacteria; the medium turns opaque; (2) The bacteria are infected with phages and die, producing new phages; the medium clears up; and (3) The medium is filtered through porcelain filter, holding back bacteria and larger objects; only the smaller phages pass through.

In early 1919, d'Herelle isolated phages from chicken feces, successfully treating a plague of chicken typhus with them. After this successful experiment on chicken, he felt ready for the first trial on humans. The first patient was healed of dysentery using phage therapy in August 1919. Many more followed. At the time, no one, not even d'Herelle, knew exactly what a phage was. D'Herelle claimed that it was a biological organism that reproduces, somehow feeding off bacteria. Others, the Nobelist Jules Bordet chief among them, theorized that phages were inanimate chemicals, enzymes specifically, that were already present in bacteria, and only trigger the release of similar proteins, killing the bacteria in the process. Due to this uncertainty, and d'Herelle using phages without much hesitation on humans, his work was under constant attack from many other scientists. It was not until the first phage was observed under an electron microscope by Helmut Ruska in 1939 that its true nature was established.

D'Herelle became widely known for his imaginative approaches to important problems in theoretical, as well as applied, microbiology. At the same time, he was widely reviled for his self-advertisement, his exaggerated claims of success and his sharp financial practices. He also had a talent for making enemies among powerful senior scientists. D'Herelle's main legacy lies in the use of phage in the molecular revolution in biology.

See Also:

Duckworth, D. H. 1976. "Who discovered bacteriophage?". Bacteriological Reviews. 40:793–802.

Ronald Aylmer Fisher (1890–1962)

Source: Wikipedia

Sir Ronald Aylmer Fisher, who published as R. A. Fisher, was an English statistician and biologist who used mathematics to combine Mendelian genetics and natural selection. This contributed to the revival of Darwinism in the early 20th century revision of the theory of evolution known as the modern synthesis. He was a prominent eugenicist in the early part of his life. In 1918 he published The Correlation Between Relatives on the Supposition of Mendelian Inheritance in 1918, in which he simultaneously resolved one of the outstanding debates in biology (the biometricians vs. the Mendelians) and introduced the idea of the analysis of variance. This paper was originally submitted to Biometrika where it was rejected, with a biological reviewer allowing that perhaps the mathematics had some value, but the biology was inconsequential while a statistical reviewer held the converse view. In 1925 he published Statistical Methods for Research Workers, one of the 20th century's most influential books on statistical methods. Fisher's method is a technique for data fusion or "meta-analysis" (analysis of analyses). This book also popularized the p-value, and it plays a central role in his approach. Fisher proposes the level p = 0.05, or a 1 in 20 chance of being exceeded by chance, as a limit for statistical significance, and applies this to a normal distribution (as a two-tailed test), thus yielding the rule of two standard deviations (on a normal distribution) for statistical significance. In 1933 he became Professor of Eugenics at University College London until 1939 when the department was dissolved. In 1935, he published by The Design of Experiments, which was also fundamental, [and promoted] statistical technique and application. In this book Fisher also outlined the Lady tasting tea, now a famous design of a statistical randomized experiment which uses Fisher's exact test and is the original exposition of Fisher's notion of a null hypothesis. In 1936 he published Has Mendel's Work Been Rediscovered?, in which he suggested that Mendel's results were too good to be true and that someone (perhaps an over-eager assistant) had fudged the results.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Sewall Wright (1889–1988)

Source: Wikipedia

Sewall Green Wright was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongside Ronald Fisher and J.B.S. Haldane, which was a major step in the development of the modern evolutionary synthesis combining genetics with evolution. He discovered the inbreeding coefficient and methods of computing it in pedigree animals. He extended this work to populations, computing the amount of inbreeding between members of populations as a result of random genetic drift, and along with Fisher he pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection, mutation, migration and genetic drift. Wright also made major contributions to mammalian and biochemical genetics. His papers on inbreeding, mating systems, and genetic drift make him a principal founder of theoretical population genetics, along with R. A. Fisher and J. B. S. Haldane. Their theoretical work is the origin of the modern evolutionary synthesis or neodarwinian synthesis. Wright was the inventor/discoverer of the inbreeding coefficient and F-statistics, standard tools in population genetics. He was the chief developer of the mathematical theory of genetic drift, which is sometimes known as the Sewall Wright effect, cumulative stochastic changes in gene frequencies that arise from random births, deaths, and Mendelian segregations in reproduction. In this work he also introduced the concept of effective population size. Wright was convinced that the interaction of genetic drift and the other evolutionary forces was important in the process of adaptation. He described the relationship between genotype or phenotype and fitness as fitness surfaces or evolutionary landscapes. On these landscapes mean population fitness was the height, plotted against horizontal axes representing the allele frequencies or the average phenotypes of the population. Natural selection would lead to a population climbing the nearest peak, while genetic drift would cause random wandering.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Hans Spemann (1869–1941)

Source: Wikipedia

Hans Spemann was a German embryologist who was awarded a Nobel Prize in Physiology or Medicine in 1935 for his discovery of the effect now known as embryonic induction, an influence, exercised by various parts of the embryo, that directs the development of groups of cells into particular tissues and organs. In 1893–1894 he moved to the University of Munich for clinical training but decided, rather than becoming a clinician, to move to the Zoological Institute at the University of Würzburg, where he remained as a lecturer until 1908. His degree in zoology, botany, and physics, awarded in 1895, followed study under Theodor Boveri, Julius Sachs and Wilhelm Röntgen. During the winter of 1896, while quarantined in a sanitarium recovering from tuberculosis, Spemann read August Weismann's book The Germ Plasm: A Theory of Heredity. He wrote in his autobiography: "I found here a theory of heredity and development elaborated with uncommon perspicacity to its ultimate consequences.....This stimulated experimental work of my own".

Spemann was appointed Professor of Zoology and Comparative Anatomy at Rostock in 1908 and, in 1914, Associate Director of the Kaiser Wilhelm Institute of Biology at Dahlem, Berlin. Here he undertook the experiments that would make him famous. Drawing upon the recent work of Warren H. Lewis[2] and Ethel Browne Harvey, he turned his skills to the gastrula, grafting a "field" of cells (the Primitive knot) from one embryo onto another. The experiments, aided by Hilde Pröscholdt (later Mangold), a Ph.D. candidate in Spemann's laboratory in Freiburg, took place over several years and were published in full only in 1924. They described an area in the embryo, the portions of which, upon transplantation into a second embryo, organized or "induced" secondary embryonic primordia regardless of location. Spemann called these areas "organiser centres" or "organisers". Later he showed that different parts of the organiser centre produce different parts of the embryo.

See Also:

Wellner, Karen, "Hans Spemann (1869-1941)". Embryo Project Encyclopedia (2010-06-15). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1688.

The Nobel Prize in Physiology or Medicine 1935: Hans Spemann

Hans Spemann. 1935. Nobel Lecture: The Organizer-Effect in Embryonic Development

Frederick Griffith (1879–1941)

Source: Wikipedia

Frederick Griffith was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function. He showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. The observation was attributed to an unidentified transforming principle or transforming factor. This was later identified as DNA. America's leading pneumococcal researcher, Oswald T. Avery, speculated that Griffith had failed to apply adequate controls. A cautious and thorough researcher, and a reticent individual, Griffith's tendency was to publish only findings that he believed truly significant, and Griffith's findings were rapidly confirmed by researchers in Avery's laboratory. His discovery was one of the first to show the central role of DNA in heredity.

Griffith's experiment showed that one strain, R (rough, non-virulent) of bacteria could be transformed to exhibit the attributes of a different strain S (smooth, virulent),through exposure to material from dead members of the other strain. Specifically, he found that if he injected live R bacteria into mice, the mice lived (no surprise, R bacteria are non-virulent). He also found that if he injected deda S bacteria into mice, the mice lived (again, no surprise, dead bacteria do not cause disease). However, if he injected mice with a combination of live R and dead S, the mice died from an infection of live S bacteria. It appeared that exposure to dead S bacteria had transformed live R into live S bacteria.

This stunning result seemed to prove that there was some non-living, physical basis to bacteria hereditary — some molecular carrier of genetic information — that was being lost from the dead S bacteria and picked up by the live R bacteria, allowing the R to transform into S. Now the question became, What is the nature of that hereditary molecule?

In 1944, work by Oswald Avery, Colin MacLeod, and Maclyn McCarty, showed that DNA is the substance that causes bacterial transformation.

See Also:

Griffith's Experiment, Explained

The Avery–MacLeod–McCarty experiment

Theophilus S. Painter (1889–1969)

Source: Wikipedia

Theophilus Shickel Painter was an American zoologist best-known for his work on the structure and function of chromosomes, especially the sex-determination genes X and Y in humans. He also carried out work in identifying genes in fruit flies (Drosophila). His work exploited the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae. Painter joined the faculty at the University of Texas in 1916 and, except for military duty during World War I, stayed there his whole career. He was, in succession, associate professor, professor and distinguished professor of zoology. He served as acting president (1944–1946) and president (1946–1952) of the University of Texas and retired from active teaching in 1966.

Harriet Creighton (1909–2004)

Courtesy of Cold Spring Harbor Laboratory Archives. Noncommercial, educational use only.

Source: Wikipedia

Harriet Baldwin Creighton was an American botanist, geneticist and educator. Born in Delavan, Illinois, Creighton graduated from Wellesley College in 1929, and went on to complete her Ph.D. at Cornell University in 1933. During her time at Cornell she worked in the field of maize cytogenetics with Barbara McClintock, the pair published a very influential paper in 1931 in which they described chromosomal crossover for the first time. This paper, part of her Ph.D. research, provided key evidence that chromosomes carried and exchanged genetic information and hence that genes for physical traits are carried on chromosomes. Barbara McClintock guided her Ph.D. research. After completing her Ph.D. she taught at Cornell University and Connecticut College, and then returned to Wellesley where she taught until her retirement in 1974; taking time from her career to serve in the U.S. Navy during World War II.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Kass, Lee B. 2005c. Harriet B. Creighton: Proud botanist. Plant Science Bulletin. 51: 118-125. Available online, December 2005:

Barbara McClintock (1902–1992)

Source: Wikipedia

Barbara McClintock was an American scientist and cytogeneticist who was awarded the 1983 Nobel Prize in Physiology or Medicine. McClintock received her PhD in botany from Cornell University in 1927. There she started her career as the leader in the development of maize cytogenetics, the focus of her research for the rest of her life. From the late 1920s, McClintock studied chromosomes and how they change during reproduction in maize. She developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas. One of those ideas was the notion of genetic recombination by crossing-over during meiosis — a mechanism by which chromosomes exchange information. In 1930, McClintock was the first person to describe the cross-shaped interaction of homologous chromosomes during meiosis. The following year, McClintock and Creighton proved the link between chromosomal crossover during meiosis and the recombination of genetic traits. They observed how the recombination of chromosomes seen under a microscope correlated with new traits. Until this point, it had only been hypothesized that genetic recombination could occur during meiosis, although it had not been shown genetically. McClintock received a fellowship from the Guggenheim Foundation that made possible six months of training in Germany during 1933 and 1934. She had planned to work with Curt Stern, who had demonstrated crossing-over in Drosophila just weeks after McClintock and Creighton had done so; however, Stern emigrated to the United States. Instead, she worked with geneticist Richard B. Goldschmidt, who was the head of the Kaiser Wilhelm Institute. She left Germany early amidst mounting political tension in Europe, and returned to Cornell, remaining there until 1936, when she accepted an Assistant Professorship offered to her by Lewis Stadler in the Department of Botany at the University of Missouri-Columbia. She produced the first genetic map for maize, linking regions of the chromosome to physical traits. She demonstrated the role of the telomere and centromere, regions of the chromosome that are important in the conservation of genetic information. She was recognized among the best in the field, awarded prestigious fellowships, and elected a member of the National Academy of Sciences in 1944.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Barbara McClintock, DNA Learning Center

Milislav Demerec (1895–1966)

Source: Wikipedia

Milislav Demerec (January 11, 1895 – April 12, 1966) was a Croatian-American geneticist, and the director of the Department of Genetics, Carnegie Institution of Washington [CIW], now Cold Spring Harbor Laboratory (CSHL) from 1941 to 1960, recruiting Barbara McClintock and Alfred Hershey. Demerec was born and raised in Kostajnica (then Austria-Hungary, now Croatia). He attended College of Agriculture in Križevci, graduating in 1916. He worked at Križevci Experiment Station, and then attended the College of Agriculture in Grignon, France after World War I. He emigrated to the United States for graduate studies in 1919. In 1919 he started his PhD at Cornell University, his work was on maize genetics and was supervised by Rollins A. Emerson. He completed his PhD in 1923 and took up a research position at the Carnegie Institution of Washington's [CIW] Department of Genetics, now Cold Spring Harbor Laboratory. He completed work from his PhD, showing that ten different alleles could cause albinism in maize kernels, the at the advice of C. W. Metz he began work on the genetics of the plant Delphinium and the fruit fly Drosophila virilis studying mosaicism.

He became a prominent Drosophila researcher and established the Drosophila Information Service newsletter in 1934 with Calvin Bridges. In 1936 he was made the assistant directory of the Department of Genetics, and the acting director in 1941 following the retirement of Albert Blakeslee. That year, he was also made director of the Biological Laboratory of the Long Island Biological Association making him the director of both Cold Spring Harbor laboratories, by 1943.

After overcoming opposition from Thomas Hunt Morgan, Demerec oversaw the completion of much of the late Calvin Bridges’s work. Demerec appointed Katherine Brehme Warren to complete The Mutants of Drosophila melanogaster (1944) and the book became a classic in the field.

In the 1940s the direction of Demerec's research changed to the genetics of bacteria and their viruses after a symposium given by Max Delbrück. During World War II he used his knowledge of bacterial genetics to increase the yield from the Penicillium. Following the war he continued to work on bacterial genetics and the problem of antibiotic resistance in E. coli, Salmonella, and Staphylococcus. In 1946 he was elected to the National Academy of Sciences, and in 1947 became the founding editor of Advances in Genetics, the first journal to review the finding of modern genetics. In the 1950s he served on the genetics panel of the National Academy of Sciences' Committee on the Biological Effects of Atomic Radiation. In 1952 he was elected to the American Philosophical Society.

See Also:

Demerec, Milislav. 1933. What is a Gene? Journal of Heredity, 24:368-378.

Richard Goldschmidt (1878–1958)

Source: Wikipedia

Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony. Controversially, Goldschmidt advanced a model of macroevolution through macromutations that is popularly known as the "Hopeful Monster" hypothesis. Goldschmidt also described the nervous system of the nematode, a piece of work that later influenced Sydney Brenner to study the wiring diagram of Caenorhabditis elegans an achievement that later won Brenner and his colleagues the Nobel Prize in 2002.

In 1903 Goldschmidt began working as an assistant to Richard Hertwig at the University of Munich, where he continued his work on nematodes and their histology, including studies of the nervous system development of Ascaris and the anatomy of Amphioxus. He founded the histology journal Archiv für Zellforschung while working in Hertwig's laboratory. Under Hertwig's influence, he also began to take an interest in chromosome behavior and the new field of genetics. In 1909 Goldschmidt became professor at the University of Munich and, inspired by Wilhelm Johannsen's genetics treatise Elemente der exakten Erblichkeitslehre, began to study sex determination and other aspects of the genetics of the gypsy moth. His studies of the gypsy moth, which culminated in his 1934 monograph Lymantria, became the basis for his theory of sex determination, which he developed from 1911 until 1931. Goldschmidt left Munich in 1914 for the position as head of the genetics section of the newly founded Kaiser Wilhelm Institute for Biology. During a field trip to Japan in 1914 he was not able to return to Germany due to the outbreak of the First World War and got stranded in the United States. He ended up in an internment camp in Fort Oglethorpe, Georgia for "dangerous Germans". After his release in 1918 he returned to Germany in 1919 and worked at the Kaiser Wilhelm Institute. Sensing that it was unsafe for him to remain in Germany he emigrated to the United States 1936, where he became professor at the University of California, Berkeley. During World War 2, the Nazi party published a propaganda poster entitled "Jewish World Domination" displaying the Goldschmidt family tree.

Goldschmidt was the first scientist to use the term "hopeful monster". He thought that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution. In his book The Material Basis of Evolution (1940), he wrote "the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation." Goldschmidt believed the large changes in evolution were caused by macromutations (large mutations). His ideas about macromutations became known as the hopeful monster hypothesis, which is considered a type of saltational evolution. According to Goldschmidt, biologists seem inclined to think that because they have not themselves seen a 'large' mutation, such a thing cannot be possible. But such a mutation need only be an event of the most extraordinary rarity to provide the world with the important material for evolution. The origin of the first eukaryotic cell might be considered an example of a Goldschmidtian hopeful monster.

See Also:

Dietrich, Michael R. 2003. Richard Goldschmidt: hopeful monsters and other 'heresies'. Nature reviews Genetics, 4:68-74.

Boris Ephrussi (1901–1979)

Source: Wikipedia

Boris Ephrussi, Professor of Genetics at the University of Paris, was a Russo-French geneticist. Boris started his scientific training as a Russian émigré in 1920. He studied the initiation and regulation of embryological processes by intracellular and extracellular factors. A major strand of his early research concerned the effect of temperature on the development of fertilized sea urchin eggs. During Ephrussi's time, writing a second dissertation was standard practice in France. Ephrussi's involved culturing tissues. Ephrussi ran into difficulties typically associated with early tissue culture techniques, but despite these obstacles Ephrussi managed to conclude from studies of brachyury in mice that intrinsic factors (i.e. genes) play a key role in development.

As the next phase of his career, Ephrussi coupled his embryological concerns with a firm conviction that one must understand the role of genes in order to decipher embryological processes. He moved to Caltech in 1934 and stayed until 1935 to learn genetics within the intellectual empire of T.H. Morgan. This move was supported by the Rockefeller Foundation. During this period he conducted important work with George Beadle, who joined him in Paris in the autumn of 1935. There they produced results from experiments with Drosophila eye transplants. This became integral to the work of Beadle and Tatum, who were working with Neurospora, and from this research developed the one gene, one enzyme hypothesis.

See Also:

Chhetri, Divyash, "Beadle and Ephrussi's Transplantation Technique for Drosophila". Embryo Project Encyclopedia (2014-06-29). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/8015.

Theodosius Dobzhansky (1900–1975)

Source: Wikipedia

Theodosius Grygorovych Dobzhanskywas a prominent Russian-American geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the unifying modern evolutionary synthesis. Dobzhansky was born in Ukraine, then part of the Russian Empire, and became an immigrant to the United States in 1927, aged 27 years old. His 1937 work Genetics and the Origin of Species became a major influence on the synthesis and was awarded the US National Medal of Science in 1964, and the Franklin Medal in 1973.

Dobzhansky immigrated to the United States in 1927 on a scholarship from the International Education Board of the Rockefeller Foundation to work and study in the United States. Arriving in New York City on December 27, he worked with Thomas Hunt Morgan at Columbia University, who had pioneered the use of fruit flies (Drosophila melanogaster) in genetics experiments. He followed Morgan to the California Institute of Technology from 1930 to 1940. On the basis of his experiments, he articulated the idea that reproductive isolation can be caused by differences in presence of microbial symbionts between populations. In 1937, he published one of the major works of the modern evolutionary synthesis, the synthesis of evolutionary biology with genetics, entitled Genetics and the Origin of Species, which amongst other things, defined evolution as "a change in the frequency of an allele within a gene pool". Dobzhansky's work was instrumental in spreading the idea that it is through mutations in genes that natural selection takes place. Also in 1937, he became a naturalized citizen of the United States. During this time, he had a very public falling out with one of his Drosophila collaborators, Alfred Sturtevant, based primarily in professional competition.

Dobzhansky's wife Natasha died of coronary thrombosis on February 22, 1969. Earlier (on June 1, 1968) Theodosius had been diagnosed with lymphocytic leukemia (a chronic form of leukemia), and had been given a few months to a few years to live. He retired in 1971, moving to the University of California, Davis where his student Francisco Jose Ayala had been made assistant professor, and where he continued working as an emeritus professor. He published one of his most famous essays "Nothing in Biology Makes Sense Except in the Light of Evolution" at this time, influenced by the paleontologist/priest Pierre Teilhard de Chardin. By 1975, his leukemia had become more severe, and on November 11 he traveled to San Jacinto, California for treatment and care. He died (of heart failure) on December 18.

See Also:

Theodosius Dobzhansky. 1973. Nothing in Biology Makes Sense except in the Light of Evolution. The American Biology Teacher, 35:125-129.

Collected papers from a NAS colloquium on Dobzhansky's Genetics and the Origin of Species

Francisco J. Ayala. 1985. Theodosius Dobzhansky 1900 – 1975. Biographical Memoirs, National Academy of Sciences.

Theodosius Dobzhansky Papers. Americal Philosophical Society

Cyril Hinshelwood (1897–1967)

Source: Wikipedia

Sir Cyril Norman Hinshelwood was an English physical chemist and a Nobel Prize laureate. During the First World War, Hinshelwood was a chemist in an explosives factory. He was a tutor at Trinity College, Oxford from 1921 to 1937 and was Dr Lee's Professor of Chemistry at the University of Oxford from 1937. He served on several Advisory Councils on scientific matters to the British Government. His early studies of molecular kinetics led to the publication of Thermodynamics for Students of Chemistry and The Kinetics of Chemical Change in 1926. With Harold Warris Thompson he studied the explosive reaction of hydrogen and oxygen and described the phenomenon of chain reaction. His subsequent work on chemical changes in the bacterial cell proved to be of great importance in later research work on antibiotics and therapeutic agents, and his book, The Chemical Kinetics of the Bacterial Cell was published in 1946, followed by Growth, Function and Regulation in Bacterial Cells in 1966. In 1951 he published The Structure of Physical Chemistry. It was republished as an Oxford Classic Texts in the Physical Sciences by Oxford University Press in 2005.

Hinshelwood applied physical-chemistry thinking to bacteria and became convinced that bacteria possessed no true genetic apparatus and therefore exhibited no formal patterns of inheritance. He argued that apparent adaptive changes in bacterial populations (e.g., the emergence of antibiotic resistance) could be explained by a process involving shifts in stable chemical equilibria, induced by exposure to diufferent environmental conditions. He referred to this process as training.

This mistaken belief dominated thought about microbial genetics until Joshua Lederberg and Edward Tatum showed that genetic recombination can be detected among bacteria.

See Also:

The Nobel Prize in Chemistry 1956 was awarded jointly to Sir Cyril Norman Hinshelwood and Nikolay Nikolaevich Semenov for their researches into the mechanism of chemical reactions.

George Beadle (1903–1989)

Source: Wikipedia

George Wells Beadle was an American scientist in the field of genetics, and Nobel Prize in Physiology or Medicine Nobel laureate who with Edward Tatum discovered the role of genes in regulating biochemical events within cells in 1958. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. In 1931 Beadle was awarded a National Research Council Fellowship at the California Institute of Technology at Pasadena, where he remained from 1931 until 1936. During this period he continued his work on Indian corn and began, in collaboration with Professors Theodosius Dobzhansky, S. Emerson, and Alfred Sturtevant, work on crossing-over in the fruit fly, Drosophila melanogaster.

In 1935 Beadle visited Paris for six months to work with Professor Boris Ephrussi at the Institut de Biologie physico-chimique. Together they began the study of the development of eye pigment in Drosophila which later led to the work on the biochemistry of the genetics of the fungus Neurospora for which Beadle and Edward Lawrie Tatum were together awarded the 1958 Nobel Prize for Physiology or Medicine. In 1936 Beadle left the California Institute of Technology to become Assistant Professor of Genetics at Harvard University. A year later he was appointed Professor of Biology (Genetics) at Stanford University and there he remained for nine years, working for most of this period in collaboration with Tatum. In 1946 he returned to the California Institute of Technology as Professor of Biology and Chairman of the Division of Biology. Here he remained until January 1961 when he was elected Chancellor of the University of Chicago and, in the autumn of the same year, President of this University.

After retiring, Beadle undertook a remarkable experiment in maize genetics. In several laboratories he grew a series of Teosinte/Maize crosses. Then he crossed these progeny with each other. He looked for the rate of appearance of parent phenotypes among this second generation. The vast majority of these plants were intermediate between maize and Teosinte in their features, but about 1 in 500 of the plants were identical to either the parent maize or the parent teosinte. Using the mathematics of Mendelian genetics, he calculated that this showed a difference between maize and teosinte of about 5 or 6 genetic loci. This demonstration was so compelling that most scientists now agree that Teosinte is the wild progenitor of maize.

See Also:

Norman H. Horowitz. 1990. George Wells Beadle 1903 – 1989. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, "George W. Beadle's One Gene-One Enzyme Hypothesis". Embryo Project Encyclopedia (2014-05-23). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7892.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Salvador Luria (1912–1991)

Source: Wikipedia

Salvador Edward Luria was an Italian microbiologist, later a naturalized U.S. citizen. He won the Nobel Prize in Physiology or Medicine in 1969, with Max Delbrück and Alfred Hershey, for their discoveries on the replication mechanism and the genetic structure of viruses. Salvador Luria also showed that bacterial resistance to viruses (phages) is genetically inherited. Luria was born Salvatore Edoardo Luria, in Turin, Italy to an influential Italian Sephardi Jewish family. His parents were Ester (Sacerdote) and Davide Luria. He attended the medical school at the University of Turin studying with Giuseppe Levi. There, he met two other future Nobel laureates: Rita Levi-Montalcini and Renato Dulbecco. He graduated from the University of Turin in 1935. From 1936 to 1937, Luria served his required time in the Italian army as a medical officer. He then took classes in radiology at the University of Rome. Here, he was introduced to Max Delbrück's theories on the gene as a molecule and began to formulate methods for testing genetic theory with the bacteriophages, viruses that infect bacteria. In 1938, he received a fellowship to study in the United States, where he intended to work with Delbrück. Soon after Luria received the award, Benito Mussolini's fascist regime banned Jews from academic research fellowships. Without funding sources for work in the U.S. or Italy, Luria left his home country for Paris, France in 1938. As the Nazi German armies invaded France in 1940, Luria fled on bicycle to Marseille where he received an immigration visa to the United States.

Luria arrived in New York City on September 12, 1940, and soon changed his first and middle names. With the help of physicist Enrico Fermi, whom he knew from his time at the University of Rome, Luria received a Rockefeller Foundation fellowship at Columbia University. He soon met Delbrück and Hershey, and they collaborated on experiments at Cold Spring Harbor Laboratory and in Delbrück's lab at Vanderbilt University. His famous experiment with Delbrück in 1943, known as the Luria–Delbrück experiment, demonstrated statistically that inheritance in bacteria must follow Darwinian rather than Lamarckian principles and that mutant bacteria occurring randomly can still bestow viral resistance without the virus being present. The idea that natural selection affects bacteria has profound consequences, for example, it explains how bacteria develop antibiotic resistance. From 1943 to 1950, he worked at Indiana University. His first graduate student was James D. Watson, who went on to discover the structure of DNA with Francis Crick. In January 1947, Luria became a naturalized citizen of the United States.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Julian Huxley (1887–1975)

Source: Wikipedia

Sir Julian Sorell Huxley was a British evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern evolutionary synthesis. He was secretary of the Zoological Society of London (1935–1942), the first Director of UNESCO, a founding member of the World Wildlife Fund and the first President of the British Humanist Association. Huxley came from the distinguished Huxley family. His brother was the writer Aldous Huxley, and his half-brother a fellow biologist and Nobel laureate, Andrew Huxley; his father was writer and editor Leonard Huxley; and his paternal grandfather was Thomas Henry Huxley, a friend and supporter of Charles Darwin and proponent of evolution. His maternal grandfather was the academic Tom Arnold, his great-uncle was poet Matthew Arnold and his great-grandfather was Thomas Arnold of Rugby School.

Huxley was one of the main architects of the modern evolutionary synthesis which took place around the time of World War II. The synthesis of genetic and population ideas produced a consensus which reigned in biology from about 1940, and which is still broadly tenable. His book Evolution: The Modern Synthesis was written while he was secretary to the Zoological Society, and made use of his remarkable collection of reprints covering the first part of the century. It was published in 1942. Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing". Huxley's main co-respondents in the modern evolutionary synthesis are usually listed as Ernst Mayr, Theodosius Dobzhansky, George Gaylord Simpson, Bernhard Rensch, Ledyard Stebbins and the population geneticists J. B. S. Haldane, Ronald Fisher and Sewall Wright.

Despite its ecstatic initial reception, the limits of Huxley's Modern Synthesis are now becoming more obvious. A particular problem is the book's completely inadequate treatment of microbial genetics:

Bacteria ... appear to be not only wholly asexual but premitotic. Their hereditary constitution is not differentiated into specialized parts with different functions. They have no genes in the sense of accurately quantized portions of hereditary substance; and therefore they have no need for the accurate division of the genetic system which is accomplished by mitosis. ... That occasional 'mutations' occur we know, but there is no ground for supposing that they are similar in nature to those of higher organisms, nor, since they are usually reversible according to conditions, that they play the same part in evolution. We must, in fact, expect that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms. J. Huxley, 1943, Evolution: The Modern Synthesis, New York: Harper & Brothers Publishers, pp. 131–132.

Although it is now clear that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms, this is not because bacteria possess no genes in the sense of accurately quantized portions of hereditary substance.

Max Delbrück (1906–1981)

Source: Wikipedia

Max Ludwig Henning Delbrück, a German–American biophysicist, helped launch the molecular biology research program in the late 1930s. He stimulated physical scientists' interest into biology, especially as to basic research to physically explain genes, mysterious at the time. Formed in 1945 and led by Delbrück along with Salvador Luria and Alfred Hershey, the Phage Group made substantial headway unraveling important aspects of genetics. The three shared the 1969 Nobel Prize in Physiology or Medicine "for their discoveries concerning the replication mechanism and the genetic structure of viruses". He was the first physicist to predict what is now called Delbrück scattering. Delbrück was born in Berlin, German Empire. His mother was granddaughter of Justus von Liebig, eminent chemist, while his father Hans Delbrück was a history professor at the University of Berlin. In 1937, Max left Nazi Germany for America—first California, then Tennessee—becoming a US citizen in 1945.

In 1937, he attained a fellowship from Rockefeller Foundation—which was launching the molecular biology research program—to research genetics of the fruit fly, Drosophila melanogaster, in California Institute of Technology's biology department, where Delbrück could blend interests in biochemistry and genetics. While at Caltech, Delbrück researched bacteria and their viruses (bacteriophages or phages). In 1939, with E.L. Ellis, he coauthored "The growth of bacteriophage", a paper reporting that the viruses reproduce in one step, not exponentially as do cellular organisms. Although Delbrück's Rockefeller Foundation fellowship expired in 1939, the Foundation matched him up with Vanderbilt University in Nashville, Tennessee, where from 1940 to 1947 he taught physics, yet had his laboratory in the biology department. In 1941, Delbrück met Salvador Luria of Indiana University who began visiting Vanderbilt. In 1942, Delbrück and Luria published on bacterial resistance to virus infection mediated by random mutation. Alfred Hershey of Washington University began visiting in 1943. The Luria–Delbrück experiment, also called the Fluctuation Test, demonstrated that Darwin's theory of natural selection acting on random mutations applies to bacteria as well as to more complex organisms. The 1969 Nobel Prize in Physiology or Medicine was awarded to both scientists in part for this work.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Erwin Schrödinger (1887–1961)

Source: Wikipedia

Erwin Rudolf Josef Alexander Schrödinger, was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in the field of quantum theory, which formed the basis of wave mechanics: he formulated the wave equation (stationary and time-dependent Schrödinger equation) and revealed the identity of his development of the formalism and matrix mechanics. Schrödinger proposed an original interpretation of the physical meaning of the wave function. In addition, he was the author of many works in various fields of physics: statistical mechanics and thermodynamics, physics of dielectrics, colour theory, electrodynamics, general relativity, and cosmology, and he made several attempts to construct a unified field theory. In his 1944 book What Is Life? Schrödinger addressed the problems of genetics, looking at the phenomenon of life from the point of view of physics.

In the book, Schrödinger introduced the paradoxical idea of an aperiodic crystal that contained genetic information in its configuration of covalent chemical bonds. [The idea of an aperiodic crystal bears a passing resemblance to the notion of dehydrated water.] In the book, Schrödinger specifically discussed the likelihood that hereditary information is somehow encoded in the molecular structure of chromosomes, noting:

It is these chromosomes, or probably only an axial skeleton fibre of what we actually see under the microscope as the chromosome, that contain in some kind of code-script the entire pattern of the individual's future development and of its functioning in the mature state. Every complete set of chromosomes contains the full code; so there are, as a rule, two copies of the latter in the fertilized egg cell, which forms the earliest stage of the future individual. In calling the structure of the chromosome fibres a code-script we mean that the all-penetrating mind, once conceived by Laplace, to which every causal connection lay immediately open, could tell from their structure whether the egg would develop, under suitable conditions, into a black cock or into a speckled hen, into a fly or a maize plant, a rhododendron, a beetle, a mouse or a woman.

In retrospect, Schrödinger's aperiodic crystal can be viewed as a well-reasoned theoretical prediction of what biologists should have been looking for during their search for genetic material. Both James D. Watson, and independently, Francis Crick, co-discoverers of the structure of DNA, credited Schrödinger's book with presenting an early theoretical description of how the storage of genetic information would work, and each respectively acknowledged the book as a source of inspiration for their initial researches. These ideas provide the conceptual foundation of molecular genetics. Schrödinger paid great attention to the philosophical aspects of science, ancient and oriental philosophical concepts, ethics, and religion. He also wrote on philosophy and theoretical biology. He is also known for his Schrödinger's cat thought-experiment.

Oswald Avery Jr. (1877–1955)

Source: Wikipedia

Oswald Theodore Avery Jr. was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller University Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment (published in 1944 with his co-workers Colin MacLeod and Maclyn McCarty) that isolated DNA as the material of which genes and chromosomes are made. For many years, genetic information was thought to be contained in cell protein. Continuing the research done by Frederick Griffith in 1927, Avery worked with MacLeod and McCarty on the mystery of inheritance. He had received emeritus status from the Rockefeller Institute in 1943, but continued working for five years, though by that time he was in his late sixties. Techniques were available to remove various organic compounds from bacteria, and if the remaining organic compounds were still able to cause R strain bacteria to transform then the substances removed could not be the carrier of genes. S-strain bacteria first had the large cellular structures removed. Then they were treated with protease enzymes, which removed the proteins from the cells before the remainder was placed with R strain bacteria. The R strain bacteria transformed, meaning that proteins did not carry the genes causing the disease. Then the remnants of the R strain bacteria were treated with a deoxyribonuclease enzyme which removed the DNA. After this treatment, the R strain bacteria no longer transformed. This indicated that DNA was the carrier of genes in cells.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Colin Munro MacLeod (1909–1972)

Source: Wikipedia

Colin Munro MacLeod was a Canadian-American geneticist. He was one of a trio of scientists who discovered that deoxyribonucleic acid, or DNA is responsible for the transformation of the physical characteristics of bacteria, which subsequently led to its identification as the molecule responsible for heredity. In his early years as a research scientist, MacLeod, with Oswald Avery and Maclyn McCarty, demonstrated DNA is the molecule responsible for bacterial transformation — and in retrospect, the physical basis of the gene. In 1941, Avery and MacLeod separated a crude extract from smooth (S) strains of Streptococcus pneumoniae, the most common cause of bacterial pneumonia. The S strain extract could convert the more benign rough (R) strains of pneumococci into the disease-causing S form. Later that year, McCarty joined the Avery laboratory, and in 1942, the group began to focus on DNA as the elusive ingredient in the S strain extract as the factor responsible for transformation of R pneumococci into S pneumococci. By early 1943, Avery, MacLeod, and McCarty had shown that DNA was the transforming factor, and in February 1944, published the first of a series of scientific papers in the Journal of Experimental Medicine demonstrating that DNA was the transforming principle. Subsequent experiments confirmed DNA as a universal bearer of genetic information. However, despite the enormous scientific importance of this work, which became known as the Avery–MacLeod–McCarty experiment, the trio did not win a Nobel Prize for their discovery.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Walsh McDermott. 1983. Colin Munro MacLeod, 1909–1972. Biographical Memoirs, National Academy of Sciences.

Maclyn McCarty (1911–2005)

Source: Wikipedia

Maclyn McCarty, who devoted his life as a physician-scientist to studying infectious disease organisms, was best known for his part in the monumental discovery that DNA, rather than protein, constituted the chemical nature of a gene. Uncovering the molecular secret of the gene in question — that for the capsular polysaccharide of pneumococcal bacteria — led the way to studying heredity not only through genetics but also through chemistry, and initiated the dawn of the age of molecular biology. McCarty was the youngest and longest surviving member of the research team responsible for this feat (known as the Avery–MacLeod–McCarty experiment), which also included Oswald T. Avery and Colin MacLeod; he died on January 2, 2005, from congestive heart failure. McCarty was born in 1911 in South Bend, Indiana, the second of four sons of a branch manager for the Studebaker Corporation while it was still a firm for horse-drawn carriages. In his teens, McCarty set himself the goal of becoming a physician-scientist, and he pursued a successful strategy to prepare for admission to, and early success in, Johns Hopkins University Medical School. As an undergraduate at Stanford University, he presciently began his studies in the nascent field of biochemistry, working with James Murray Luck on protein turnover in the liver. In 1937, he began his clinical training in pediatrics at the Harriet Lane Service at Johns Hopkins University. There McCarty developed a special interest in infectious diseases — in particular, antibacterial sulfonamide drug treatments that were just entering medicine — which he subsequently pursued by moving to New York University to work with William Tillett. A National Research Council Fellowship in the medical sciences and an opening in Oswald T. Avery's laboratory spurred his move to Rockefeller University in 1941. At that time, research in the Avery laboratory was focused on the pneumococcal transformation, the heritable alteration of a pneumococcal strain from a nonvirulent rough form to a virulent smooth encapsulated form. McCarty's arrival at the Rockefeller Institute in September 1941 marked 13 years since this discovery, also known as the Griffith phenomenon.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Lederberg, Joshua, and Gotschlich, Emil C. 2005. A Path to Discovery: The Career of Maclyn McCarty. PLoS Biology, 3:e341.

Joshua Lederberg (1925–2008)

Source: Wikipedia

Joshua Lederberg was an American molecular biologist known for his work in microbial genetics, artificial intelligence, and the United States space program. He was 33 years old when he won the 1958 Nobel Prize in Physiology or Medicine for discovering that bacteria can mate and exchange genes (bacterial conjugation). He shared the prize with Edward Tatum and George Beadle, who won for their work with genetics. He enrolled in Columbia University in 1941, majoring in zoology. Under the mentorship of Francis J. Ryan, he conducted biochemical and genetic studies on the bread mold Neurospora crassa. Intending to receive his MD and fulfill his military service obligations, Lederberg worked as a hospital corpsman during 1943 in the clinical pathology laboratory at St. Albans Naval Hospital, where he examined sailors' blood and stool samples for malaria. He went on to receive his undergraduate degree in 1944.

Joshua Lederberg began medical studies at Columbia's College of Physicians and Surgeons while continuing to perform experiments. Inspired by Oswald Avery's discovery of the importance of DNA, Lederberg began to investigate his hypothesis that, contrary to prevailing opinion, bacteria did not simply pass down exact copies of genetic information, making all cells in a lineage essentially clones. After making little progress at Columbia, Lederberg wrote to Edward Tatum, Ryan's post-doctoral mentor, proposing a collaboration. In 1946 and 1947, Lederberg took a leave of absence to study under the mentorship of Tatum at Yale University. Lederberg and Tatum showed that the bacterium Escherichia coli entered a sexual phase during which it could share genetic information through bacterial conjugation. With this discovery and some mapping of the E. coli chromosome, Lederberg was able to receive his Ph.D. from Yale University in 1947. Instead of returning to Columbia to finish his medical degree, Lederberg chose to accept an offer of an assistant professorship in genetics at the University of Wisconsin–Madison. In 1951, Lederberg and Norton Zinder showed that genetic material could be transferred from one strain of the bacterium Salmonella typhimurium to another using viral material as an intermediary step. This process is called transduction.

In 1958, Joshua Lederberg received the Nobel Prize and moved to Stanford University, where he was the founder and chairman of the Department of Genetics. In 1978, he became the president of Rockefeller University, until he stepped down in 1990 and became professor-emeritus of molecular genetics and informatics at Rockefeller University, considering his extensive research and publications in these disciplines. Throughout his career, Lederberg was active as a scientific advisor to the U.S. government.

See Also:

Walter Bodmer and Ann Ganesan. 2011. Joshua Lederberg. 23 May 1925 – 2 February 2008. Biographical Memoirs of Fellows of the Royal Society. 57: 229–251. doi:10.1098/rsbm.2010.0024

Joshua Lederberg Papers 1904-2008

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

S. Gaylen Bradley. 2009. Joshua Lederberg 1925 – 2008. National Academy of Sciences, Biographical Memoirs

Edward Tatum (1909–1975)

Source: Wikipedia

Edward Lawrie Tatum was an American geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Beadle for showing that genes control individual steps in metabolism. The other half of that year's award went to Joshua Lederberg. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments, published in 1941, led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. This became a fundamental concept in physiological genetics. Tatum went on to study genetics in bacteria. An active area of research in his laboratory was to understand the basis of Tryptophan biosynthesis in Escherichia coli. Later, Tatum and his student Joshua Lederberg showed that E. coli could share genetic information through recombination. This became a fundamental concept in microbial genetics.

See Also:

Joshua Lederberg. 1990. Edward Lawrie Tatum 1909 – 1975. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Ching Chun Li (1912–2003)

Source: Wikipedia

Ching Chun Li was a respected American population geneticist and human geneticist. Li was best known for his book An Introduction to Population Genetics and his teaching in human genetics. Ching Chun Li was born on October 27, 1912, in Taku, Tianjin, China. He received his BS degree in agronomy from the University of Nanking in 1936 and a PhD in plant breeding and genetics from Cornell University in 1940. He worked as post-doctorate fellows at Columbia University and North Carolina State University from 1940 to 1941. Li returned to China at the age of 30 and became the Professor of Genetics and Biometry at University of Nanking, his alma mater, in 1943. After World War II, he moved to Beijing for a Professorship of Agronomy at Peking University in 1946, where he finished An Introduction to Population Genetics in 1948. The book was the first notable publication where the population-genetics ideas of Ronald Fisher, Sewall Wright, and J. B. S. Haldane were brought together, synthesized, and presented in a coherent and readily understood manner.

See Also:

Aravinda Chakravarti. 2004. Ching Chun Li (1912–2003): A Personal Remembrance of a Hero of Genetics. The American Journal of Human Genetics, 74:789-792.

Eliot B. Spiess. 2005. Remembrance of Ching Chun Li, 1912–2003. Genetics, 169:9-11.

Erwin Chargaff (1905–2002)

Source: Wikipedia

Erwin Chargaff (11 August 1905 – 20 June 2002) was an Austro-Hungarian biochemist that immigrated to the United States during the Nazi era and was a professor of biochemistry at Columbia University medical school. Through careful experimentation, Chargaff made two observations that helped to disprove the tetranucleotide model of DNA. Under the tetranucleotide hypothesis, it was assumed that DNA was built as a simple repeating polymer of units consisting of one adenine, one thymine, one cytosine, and one guanine. Such a structure would mean that all DNA molecules has essentially the same structure, differeing only in length. Such a molecule would be incapable of carrying hereditary information. Chargaff's observations: (1) the percent nucleotide composition of DNA was not exactly 25% of each nucleotide, (2) the percent nucleotide composition of DNA differed (slightly) from one species to another, and (3) the percent nucleotide composition of DNA was constant within a species. He also observed regular numerical patterns in the nucleotide makeup of any DNA sample. The two best remembered patterns are that, in any DNA sample, the amount of adenine always equals the amount of thymine, and the amount of guanine always equals the amount of cytosine. These observations, especially the A-T and C-G equalities, helped Watson and Crick devise the double-helix model of DNA. Chargaff had a quick wit and a sharp pen and he was not impressed with advances made through theory rather than through laboratory work. He once commented that Molecular biology is essentially the practice of biochemistry without a license.

James Dewey Watson (1928–      )

Source: Wikipedia

James Dewey Watson is an American molecular biologist, geneticist and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick. Watson, Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". From 1956 to 1976, Watson was on the faculty of the Harvard University Biology Department, promoting research in molecular biology. From 1968 he served as director of Cold Spring Harbor Laboratory (CSHL), greatly expanding its level of funding and research. At CSHL, he shifted his research emphasis to the study of cancer, along with making it a world leading research center in molecular biology. In 1994, he started as president and served for 10 years. He was then appointed chancellor, serving until he resigned in 2007. Between 1988 and 1992, Watson was associated with the National Institutes of Health, helping to establish the Human Genome Project.

Francis Crick (1916–2004)

Source: Wikipedia

Francis Harry Compton Crick was a British molecular biologist, biophysicist, and neuroscientist, most noted for being a co-discoverer of the structure of the DNA molecule in 1953 with James Watson. Together with Watson and Maurice Wilkins, he was jointly awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". Crick was an important theoretical molecular biologist and played a crucial role in research related to revealing the helical structure of DNA. He is widely known for use of the term "central dogma" to summarize the idea that genetic information flow in cells is essentially one-way, from DNA to RNA to protein. During the remainder of his career, he held the post of J.W. Kieckhefer Distinguished Research Professor at the Salk Institute for Biological Studies in La Jolla, California. His later research centered on theoretical neurobiology and attempts to advance the scientific study of human consciousness. He remained in this post until his death; "he was editing a manuscript on his death bed, a scientist until the bitter end" according to Christof Koch.

Carl Woese (1928–2012)

Source: Wikipedia

Carl Richard Woese was an American microbiologist and biophysicist. Woese is famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese which revolutionized the discipline of microbiology. He was also the originator of the RNA world hypothesis in 1967, although not by that name. He held the Stanley O. Ikenberry Chair and was professor of microbiology at the University of Illinois at Urbana–Champaign. For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their biochemistry, morphology and metabolism. In a highly influential 1962 paper, Roger Stanier and C. B. van Niel first established the division of cellular organization into prokaryotes and eukaryotes, defining prokaryotes as those organisms lacking a cell nucleus. Stanier and Van Niel's concept was quickly accepted as the most important distinction among organisms; yet they were nevertheless skeptical of microbiologists' attempts to construct a natural phylogenetic classification of bacteria. However, it became generally assumed that all life shared a common prokaryotic (implied by the Greek root pro- (before, in front of) ancestor. In 1977, Carl Woese and George E. Fox experimentally disproved this universally held hypothesis about the basic structure of the tree of life. Woese and Fox discovered a kind of microbial life which they called the “archaebacteria” (Archaea). They reported that the archaebacteria comprised "a third kingdom" of life as distinct from bacteria as plants and animals. Having defined Archaea as a new "urkingdom" (later domain) which were neither bacteria nor eukaryotes, Woese redrew the taxonomic tree. His three-domain system, based on phylogenetic relationships rather than obvious morphological similarities, divided life into 23 main divisions, incorporated within three domains: Bacteria, Archaea, and Eucarya.

See Also:

Looking in the Right Direction: Carl Woese and the New Biology

Pierre-Louis Maupertuis (1698–1759)

Source: Wikipedia

Pierre Louis Moreau de Maupertuis was a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Prussian Academy of Science, at the invitation of Frederick the Great. His work in natural history is interesting in relation to modern science, since he touched on aspects of heredity and the struggle for life. Some historians of science point to his work in biology as a significant precursor to the development of evolutionary theory, specifically the theory of natural selection. Other writers contend that his remarks are cursory, vague, or incidental to that particular argument. Mayr's verdict was "He was neither an evolutionist, nor one of the founders of the theory of natural selection [but] he was one of the pioneers of genetics". Maupertuis espoused a theory of pangenesis, postulating particles from both mother and father as responsible for the characters of the child. Bowler credits him with studies on heredity, with the natural origin of human races, and with the idea that forms of life may have changed with time.

Joseph Gottlieb Kölreuter (1733–1806)

Source: Wikipedia

Joseph Gottlieb Kölreuter, also spelled Koelreuter or Kohlreuter, was a German botanist who pioneered the study of plant fertilization, hybridization and was the first to detect self-incompatibility. He was an observer as well as a rigorous experimenter who used careful crossing experiments although he did not inquire into the nature of heritability. Kölreuter was the oldest of three sons of an apothecary in Karlsruhe, Germany, and grew up in Sulz. He took an early interest in natural history and made a collection of local insects. At the age of fifteen he went to study medicine at the University of Tübingen under physician and botanist Johann Georg Gmelin who had returned from St. Petersburg. Gmelin had an interest in floral biology and he reprinted a work by Rudolf Jakob Camerarius (who also taught at Tübingen) who was the first to demonstrate sexual reproduction in plants. In his inaugural address in 1749 Gmelin talked the need for research on the origin of new species by hybridization. Kölreuter major works were produced as four reports Vorlaufige Nachricht von einigen das Geschlecht der Pflanzen betreffenden Versuchen und Beobachtungen (1761), Fortsetzung (1763), Zweyte Fortsetzung (1764), and Dritte Fortsetzung (1766). In all he conducted nearly 500 different hybridization experiments across 138 species and examined the pollen characteristics of over a 1000 plant species.

See Also:

Ernst Mayr. 1986. Joseph Gottlieb Kölreuter's Contributions to Biology. Osiris, 2:135-176.

Thomas Andrew Knight (1759–1838)

Source: Wikipedia

Thomas Andrew Knight was a horticulturalist and botanist. He served as the 2nd President of the Royal Horticultural Society (1811-1838). He attended Balliol College, Oxford. After graduation, he took up the study of horticulture. Attention was first called to his work in 1795 by the publication of the results of his research into the propagation of fruit trees and the diseases prevalent among them. He used 10,000 acres (4,000 ha) of land he inherited to conduct breeding of plants including strawberries, cabbages and peas and built an extensive greenhouse. In 1797 he published his Treatise on the Culture of the Apple and Pear, and on the Manufacture of Cider and Perry, a work which passed through several editions. He was one of the leading students of horticulture in the eighteenth and nineteenth centuries, but his personal papers disappeared after his death. Knight performed basic physiological experiments on plants, which work had been performed before only rarely. He elucidated the effects of gravity on seedlings and how decay in fruit trees was passed on by grafting. In many respects his work looked back to that of Rev. Stephen Hales. His goals were always strictly practical, aiming to improve useful food plants by breeding for better qualities. The Downton strawberry was the ancestor of most important modern strawberries until recent times.

It is not widely known that Knight studied variation in peas and found many of the same results as Mendel, but he failed to make the same imaginative leap about how these changes took place. In 1799 he wrote:

But, as I foresaw that several years must elapse, before the success or failure of this process [note: "this process" refers to Knight's goal of producing improved varieties of apples] could possibly be ascertained, I wished, in the interval, to see what would be its effects on annual plants. Amongst these, none appeared so well calculated to answer my purpose as the common pea; not only because I could obtain many varieties of this plant, of different forms, sizes, and colours; but also, because the structure of its blossom, by preventing the ingress of insects and adventitious farina, has rendeed its varieties remarkably permanent. Thomas Andrew Knight. 1799. An Account of Some Experiments on the Fecundation of Vegetables. Philosophical Transactions of the Royal Society of London, 89:195-204.

Knight intentionally shut himself off from outside scientific influences. He refused to read anyone else's scientific papers until Sir Joseph Banks, with whom he had a voluminous correspondence, persuaded him to do so. Knight reported on all his work in the Transactions of the Royal Society of London.

See Also:

Conway Zirkle. 1951. Gregor Mendel & His Precursors. ISIS, 42:97-104.

Charles A Shull and J. Fisher Stanfield. Thomas Andrew Knight, In memoriam. Plant Phyisiology, 14:1-8.

Thomas Andrew Knight. 1799. An Account of Some Experiments on the Fecundation of Vegetables. Philosophical Transactions of the Royal Society of London, 89:195-204.

Carl Friedrich von Gärtner (1772–1850)

Source: Wikipedia

Carl Friedrich von Gärtner (or Karl Friedrich von Gaertner) was a well-known German botanist, and the son of Joseph Gaertner. He was a pioneer in the study of hybrids, and he is considered an important influence for Gregor Mendel. Gärtner, who was a protestant, challenged the doctrine of Carl Linnaeus of the "new special creation" which stated that new species of vegetation could arise through hybridization. He defended the stability of species, and argued that although the transmutation of species was evidently possible, the new species would not last because of a law of reversion which prevented them from spreading freely.

In Experiments on Plant Hybridization, Mendel wrote:

Gärtner by the results of [his] transformation experiments, was led to oppose the opinion of those naturalists who dispute the stability of plant species and believe in a continuous evolution of vegetation. He perceives in the complete transformation of one species into another an indubitable proof that species are fixed within limits beyond which they cannot change. Although this opinion cannot be unconditionally accepted we find on the other hand in Gärtner’s experiments a noteworthy confirmation of that supposition regarding variability of cultivated plants which has already been expressed.

Charles Darwin (1809–1882)

Source: Wikipedia

Charles Robert Darwin was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution. He established that all species of life have descended over time from common ancestors and, in a joint publication with Alfred Russel Wallace, introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. Darwin published his theory of evolution with compelling evidence in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species. By the 1870s, the scientific community and much of the general public had accepted evolution as a fact. However, many favoured competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed in which natural selection was the basic mechanism of evolution. In modified form, Darwin's scientific discovery is the unifying theory of the life sciences, explaining the diversity of life.

See Also:

Darwin Online: The world's largest and most widely used resource on Darwin, containing his complete publications, his private papers and manuscripts, and much supplementary material.

Gregor Mendel (1822–1884)

Source: Wikipedia

Gregor Johann Mendel was a scientist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire (today's Czech Republic) and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance.

See Also:

Vítězslav Orel. 1996. Gregor Mendel: The First Geneticist. Oxford: Oxford University Press. 376 pp.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — a facsimile of the original publication in German.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — translated into English.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — translated into English, with sidenote annotations.

Robin Marantz Henig. 2001. The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics. New York: Mariner Books. 304 pp.

Simon Mawer. 2006. Gregor Mendel: Planting the Seeds of Genetics. Harry N Abrams. 176pp.

Andrei, Amanda, ""Experiments in Plant Hybridization" (1866), by Johann Gregor Mendel". Embryo Project Encyclopedia (2013-09-04). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/6240.

Francis Galton (1822–1911)

Source: Wikipedia

Sir Francis Galton was an English Victorian statistician, progressive, polymath, sociologist, psychologist, anthropologist, eugenicist, tropical explorer, geographer, inventor, meteorologist, proto-geneticist, and psychometrician. He was knighted in 1909. Galton produced over 340 papers and books. He also created the statistical concept of correlation and widely promoted regression toward the mean. He was the first to apply statistical methods to the study of human differences and inheritance of intelligence, and introduced the use of questionnaires and surveys for collecting data on human communities, which he needed for genealogical and biographical works and for his anthropometric studies.

See Also:

GALTON.ORG — An extensive on-line collection, providing a biography, Galton's collected works, and more.

The Francis Galton Papers: A collection of digitized resources maintained by the Wellcome Library (part of the Wellcome Trust)

Carl Nägeli (1817–1891)

Source: Wikipedia

Carl Wilhelm von Nägeli was a Swiss botanist. He studied cell division and pollination but became known as the man who discouraged Gregor Mendel from further work on genetics. He rejected natural selection as a mechanism of evolution, favouring orthogenesis driven by a supposed "inner perfecting principle". The writer Simon Mawer, in his book Gregor Mendel: Planting the Seeds of Genetics (2006), gives us an interesting and detailed account of Nägeli's correspondence with Mendel. Mawer underlines that, at the time Nägeli was writing to the friar from Moravia, Nägeli "must have been preparing his great work entitled A mechanico-physiological theory of organic evolution (published in 1884, the year of Mendel's death) in which he proposes the concept of the 'idioplasm' as the hypothetical transmitter of inherited characters". Mawer notes that, in this Nägeli book, there is not a single mention of the work of Gregor Mendel. That prompted him to write: "We can forgive von Nägeli for being obtuse and supercilious. We can forgive him for being ignorant, a scientist of his time who did not really have the equipment to understand the significance of what Mendel had done despite the fact that he (von Nägeli) speculated extensively about inheritance. But omitting an account of Mendel's work from his book is, perhaps, unforgivable." (Mawer 2006, p. 81)

Friedrich Miescher (1844–1895)

Source: Wikipedia

Johannes Friedrich Miescher was a Swiss physician and biologist. He was the first researcher to isolate nucleic acid. Miescher isolated various phosphate-rich chemicals, which he called nuclein (now nucleic acids), from the nuclei of white blood cells in 1869 in Felix Hoppe-Seyler's laboratory at the University of Tübingen, Germany, paving the way for the identification of DNA as the carrier of inheritance. The significance of the discovery, first published in 1871, was not at first apparent, and it was Albrecht Kossel who made the initial inquiries into its chemical structure. Later, Friedrich Miescher raised the idea that the nucleic acids could be involved in heredity.

See Also:

Ralf Dahm. 2008. Discovering DNA: Friedrich Miescher and the early years of nucleic acid research. Human Genetics, 122:565. doi:10.1007/s00439-007-0433-0

William Keith Brooks (1848–1908)

Source: Wikipedia

William Keith Brooks received a Bachelor of Arts degree from Williams College in 1870 and a PhD from Harvard in 1875. With the opening of The Johns Hopkins University in 1876, Brooks received one of the university's initial fellowships and he quickly advanced within the organization, ultimately serving as Professor of Zoology and Head of the Biological Department. At the young age of 36 he was elected a member of the National Academy. He was chosen as a member of the American Philosophical Society in 1886 and of the Academy of Natural Science in 1887. Although many of Brooks' scientific contributions represent solid, nineteeth-century work, his most lasting effect came from his long-standing conviction that the processes of heredity were themselves a proper subject of investigation. In 1876 he wrote a paper entitled "A Provisional Hypothesis of Pangenesis" and he gave the subject a book-length treatment in his The Law of Heredity. A Study of the Cause of Variation and the Origin of Living Organisms. He was known as both a man of deep, abstract thought and an excellent teacher, as evidenced by the fact that many of the still well-known pioneers of genetics had, at one time or another, studied with him: viz. Thomas Morgan, E. B. Wilson, and William Bateson.

Walther Flemming (1843–1905)

Source: Wikipedia

Walther Flemming was a German biologist and a founder of cytogenetics. Flemming trained in medicine at University of Rostock, graduating in 1868. Afterwards, he served in 1870–71 as a military physician in the Franco-Prussian War. From 1873 to 1876 he worked as a teacher at the University of Prague. In 1876 he accepted a post as a professor of anatomy at the University of Kiel. He became the director of the Anatomical Institute and stayed there until his death. With the use of aniline dyes he was able to find a structure which strongly absorbed basophilic dyes, which he named chromatin. He identified that chromatin was correlated to threadlike structures in the cell nucleus – the chromosomes (meaning coloured bodies), which were named thus later by German anatomist Wilhelm von Waldeyer-Hartz (1841–1923). The Belgian scientist Edouard Van Beneden (1846–1910) had also independently observed chromosomes. Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread. However, he did not see the splitting into identical halves, the daughter chromatids. He studied mitosis both in vivo and in stained preparations, using as the source of biological material the fins and gills of salamanders. These results were published first in 1878 and in 1882 in the seminal book Zellsubstanz, Kern und Zelltheilung (Cell substance, nucleus and cell division). On the basis of his discoveries, Flemming surmised for the first time that all cell nuclei came from another predecessor nucleus (he coined the phrase omnis nucleus e nucleo, after Virchow's omnis cellula e cellula).

See Also:

Neidhard Paweletz. 2001. Walther Flemming: pioneer of mitosis research. Nature Reviews Molecular Cell Biology, 2:72-75. | doi:10.1038/35048077

Eduard Strasburger (1844–1912)

Source: Wikipedia

Eduard Adolf Strasburger was a Polish-German professor who was one of the most famous botanists of the 19th century. Strasburger studied biological sciences in Paris, Bonn and Jena, receiving a PhD in 1866 after working with Nathanael Pringsheim. In 1868 he taught at the University of Warsaw. In 1869 he was appointed professor of botany at the University of Jena. Since 1881 he was head of the Botanisches Institut at the University of Bonn. Together with Walther Flemming, and Edouard van Beneden he elucidated chromosome distribution during cell division.

Édouard van Beneden (1846–1910)

Source: Wikipedia

Édouard Joseph Louis Marie Van Beneden was a Belgian embryologist, cytologist and marine biologist. He was professor of zoology at the University of Liège. He contributed to cytogenetics by his works on the roundworm Ascaris. In this work he discovered and described the process of meiosis — a two-cell-division process by which cells reduce the number of chromosomes in preparation for the production of gametes. Van Beneden also elucidated, together with Walther Flemming and Eduard Strasburger, the essential facts of mitosis — the single-cell-division process that distributes equal chromosome complements to each of the two daughter cells.

Wilhelm von Waldeyer (1836–1921)

Source: Wikipedia

Heinrich Wilhelm Gottfried von Waldeyer-Hartz was a German anatomist, famous for consolidating the neuron theory of organization of the nervous system and for naming the chromosome. He is also remembered in two macroanatomical structures of the human body which were named after him: Waldeyer's tonsillar ring (the lymphoid tissue ring of the naso- and oropharynx) and Waldeyer's glands (of the eyelids). Waldeyer also studied the basophilic stained filaments which had been found (by his colleague of Kiel, Walther Flemming) to be the main constituents of chromatin, the material inside the cell nucleus. Although the full significance of chromosomes for genetics and for cell biology was still to be discovered, these filaments were known to be involved in the phenomenon of cell division discovered by Flemming, named mitosis, as well as in meiosis. In 1888, Waldeyer coined the term chromosome — colored body — to describe them.

See Also:

T. Cremer and C. Cremer. 1988. Centennial of Wilhelm Waldeyer’s introduction of the term “chromosome” in 1888. Cytogenetics and Cell Genetics, 48:66–67. (DOI:10.1159/000132591)

Waldeyer's 1888 paper in which he uses the word chromosome: Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen.

Oscar Hertwig (1849–1922)

Source: Wikipedia

Oscar Hertwig was a German zoologist and professor, who also wrote about the theory of evolution circa 1916, over 55 years after Charles Darwin's book The Origin of Species. Oscar Hertwig was a leader in the field of comparative and causal animal-developmental history. He also wrote a leading textbook. By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell. He recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he published his findings that fertilization includes the penetration of a spermatozoon into an egg cell. Oscar Hertwig experiments with frog eggs revealed the 'long axis rule', or Hertwig rule. According to this rule cell divides along its long axis (1884). While Oscar was well interested in developmental biology, he was opposed to chance as assumed in Charles Darwin´s theory. His most important theoretical book was: Das Werden der Organismen, eine Widerlegung der Darwinschen Zufallslehre (Jena, 1916) (translation: The Origin of Organisms – a Refutation of Darwin's Theory of Chance).

See Also:

Brind'Amour, Katherine,, Garcia, Benjamin, "Wilhelm August Oscar Hertwig (1849-1922)". Embryo Project Encyclopedia (2007-11-01). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1707.

Churchill, F B (1970), "Hertwig, Weismann, and the meaning of reduction division circa 1890.", Isis; an international review devoted to the history of science and its cultural influences, 61:429–57.

August Weismann (1834–1914)

Source: Wikipedia

August Friedrich Leopold Weismann was a German evolutionary biologist. Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg. His main contribution involved his Germ Plasm Theory, at one time also known as Weismannism, according to which inheritance (in a multicellular organism) only takes place by means of the germ cells — the gametes such as egg cells and sperm cells. Other cells of the body — somatic cells — do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. The idea of the Weismann barrier is central to the modern evolutionary synthesis, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection. Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time".

See Also:

Essays Upon Heredity — a collection of Weismann's writing on hereditary issues.

Yawen Zou. 2015. The Germ-Plasm: a Theory of Heredity (1893), by August Weismann. The Embryo Project Encyclopedia.

Edwin G. Conklin. 1915. August Weismann. Proceedings of the American Philosophical Society, 54:3-12.

Edmund Beecher Wilson (1856–1939)

Source: Wikipedia

Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell in Development and Inheritance. He and Nettie Maria Stevens were the first researchers to describe the chromosomal basis of sex, but they conducted their research independently of each other. Wilson is credited as America's first cell biologist. In 1898 he used the similarity in embryos to describe phylogenetic relationships. By observing spiral cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells and concluded that all these organisms must have a common ancestor.

William Bateson (1861–1926)

Source: Wikipedia

William Bateson was an English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscovery in 1900 by Hugo de Vries and Carl Correns. Bateson first suggested using the word "genetics" to describe the study of inheritance and the science of variation in a personal letter to Adam Sedgwick who had been Darwin's professor), dated 18 April 1905. Bateson first used the term "genetics" publicly at the Third International Conference on Plant Hybridization in London in 1906.

Erich von Tschermak (1864–1933)

Source: Wikipedia

Erich Tschermak, Edler von Seysenegg was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gustav Tschermak von Seysenegg. His maternal grandfather was the famous botanist, Eduard Fenzl, who taught Gregor Mendel botany during his student days in Vienna.

Carl Correns (1864–1933)

Source: Wikipedia

Carl Erich Correns was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, and for his rediscovery of Gregor Mendel's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich Tschermak von Seysenegg and Hugo de Vries, and the agronomist William Jasper Spillman. Carl Correns conducted much of the foundational work for the field of genetics at the turn of the 20th century. He rediscovered and independently verified the work of Mendel in a separate model organism. He also discovered cytoplasmic inheritance, an important extension of Mendel's theories, which demonstrated the existence of extra-chromosomal factors on phenotype. Most of Correns' work went unpublished however, and was destroyed in the Berlin bombings of 1945.

Hugo de Vries (1848–1935)

Source: Wikipedia

Hugo Marie de Vries was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution. In 1889, De Vries published his book Intracellular Pangenesis, in which, based on a modified version of Charles Darwin's theory of Pangenesis of 1868, he postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles. He called these units pangenes, a term 20 years later to be shortened to genes by Wilhelm Johannsen.

See Also:

Ralph E. Cleland. 1936. Hugo de Vries. Proceedings of the American Philosophical Society, 76:248-250.

Theodor Boveri (1862–1915)

Source: Embryo Project

Theodor Heinrich Boveri was a German biologist. He was notable for first hypothesising the cellular processes that cause cancer. Boveri's work with sea urchins showed that it was necessary to have all chromosomes present in order for proper embryonic development to take place. This discovery was an important part of the Boveri–Sutton chromosome theory, which identifies chromosomes as the carriers of genetic material. The theory correctly explains the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors (particles) required by Mendel's laws. The chromosome theory of inheritance is credited to papers by Walter Sutton in 1902 and 1903, as well as to independent work by Theodor Boveri during roughly the same period. Boveri's thoughts are summarized in his book Ergebnisse über die Konstitution der chromatischen Substanz des Zellkerns (Results on the constitution of the chromatic substance of the cell nucleus), Jena: Verlag von Gustav Fischer, 1904. His other significant discovery was the centrosome (1888), which he described as the especial organ of cell division. Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode Parascaris.

Archibald Garrod (1857–1938)

Source: Wikipedia

Sir Archibald Edward Garrod was an English physician who pioneered the field of inborn errors of metabolism. He also discovered alkaptonuria, understanding its inheritance. He served as Regius Professor of Medicine at the University of Oxford from 1920 to 1927. Garrod is best known for his scientific study of inborn errors of metabolism. He developed an increasing interest in chemical pathology, and investigated urine chemistry as a reflection of systemic metabolism and disease. This research, combined with the new understanding of Mendelian inheritance, evolved from an investigation of a few families with an obscure and not very dangerous disease (alkaptonuria) to the realization that a whole territory of mysterious diseases might be understood as inherited disorders of metabolism. Working with William Bateson, Garrod came to understand the pattern of alkaptonuria appearance in children based on Mendelian principles. Once he applied Mendel’s concepts to alkaptonuria, he published a paper in 1902 called The Incidence of Alkaptonuria: A Study of Chemical Individuality. In the paper, Garrod explains how he came to understand the condition and speculates as to its causes. He cites various case studies and compares alkaptonuria to albinism in how it is inherited. He summarized his thoughts on the relationship of inheritance to metabolic disease in his book Inborn Errors of Metabolism .

See Also:

F. G. Hopkins. 1938. Archibald Edward Garrod. 1857–1936. Biographical Memoirs of fellows of the Royal Society, 2:225–228.

Krishna Dronamraju. 1992. BIOGRAPHY Profiles in Genetics: Archibald E. Garrod (1857-1936). american Journal of Human Genetics, 51:216-219.

Raphael Weldon (1860–1906)

Source: Wikipedia

Walter Frank Raphael Weldon, generally called Raphael Weldon, was an English evolutionary biologist and a founder of biometry. He was the joint founding editor of Biometrika, with Francis Galton and Karl Pearson. Medicine was his intended career and he spent the academic year 1876-1877 at University College London. Among his teachers were the zoologist E. Ray Lankester and the mathematician Olaus Henrici. In the following year he transferred to King's College London and then to St John's College, Cambridge in 1878. There Weldon studied with the developmental morphologist Francis Balfour who influenced him greatly; Weldon gave up his plans for a career in medicine. In 1881 he gained a first-class honours degree in the Natural Science Tripos; in the autumn he left for the Naples Zoological Station to begin the first of his studies on marine biological organisms.

Upon returning to Cambridge in 1882, he was appointed university lecturer in Invertebrate Morphology. Weldon's work was centred on the development of a fuller understanding of marine biological phenomena and selective death rates of these organisms. In 1889 Weldon succeeded Lankester in the Jodrell Chair of Zoology at University College London, and was elected to the Royal Society in 1890. Royal Society records show his election supporters included the great zoologists of the day: Huxley, Lankester, Poulton, Newton, Flower, Romanes and others. His interests were changing from morphology to problems in variation and organic correlation. He began using the statistical techniques that Francis Galton had developed for he had come to the view that "the problem of animal evolution is essentially a statistical problem." Weldon began working with his University College colleague, the mathematician Karl Pearson. Their partnership was very important to both men and survived Weldon's move to the Linacre Chair of Zoology at Oxford University in 1899. In the years of their collaboration Pearson laid the foundations of modern statistics.

In 1900 the work of Gregor Mendel was rediscovered and this precipitated a conflict between Weldon and Pearson on the one side and William Bateson on the other. Bateson, who had been taught by Weldon, took a very strong line against the biometricians. This bitter dispute ranged across substantive issues of the nature of evolution and methodological issues such as the value of the statistical method. In The Origins of Theoretical Population Genetics, William Provine gives a detailed account of the controversy. The debate lost much of its intensity with the death of Weldon in 1906, though the general debate between the biometricians and the Mendelians continued until the creation of the modern evolutionary synthesis in the 1930s.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Online Weldon Biography

Weldon, Walter Frank Raphael. Encyclopedia of Mathematics

P Froggatt and N C Nevin. 1971. The 'law of ancestral heredity' and the Mendelian-ancestrian controversy in England, 1889-1906. Journal of Medical Genetics, 8:1-36.

Weldon, W. F. R. 1902. Mendel's laws of alternative inheritance in peas. Biometrika, 1:228-254.

Karl Pearson. 1906. "Walter Frank Raphael Weldon 1860-1906," Biometrika, 5:1-52.

Clarence Erwin McClung (1870–1946)

Source: Wikipedia

Clarence Erwin (CE) McClung was an American zoologist of wide-ranging interests. Although born in California, he spent much of his early life in Kansas. He originally studied pharmacy at Kansas University, receiving the Ph.G. degree in 1892. He taught pharmacy at the University for a year, but then his interest shifted to more general biological questions and he reenrolled as a student. From Kansas University he received the A.B. degree in 1896, the A.M. in 1898, and the Ph.D. in 1902. CE McClung made important contributions to early genetics, but he was also a general zoologist and paleontologist who received all of his degrees from Kansas and then spent his early career on the faculty there, ultimately assuming the positions of chair of the zoology department, curator of vertebrate paleontology, and even acting dean of the medical school. Early in his career, he undertook an investigation of spermatogenesis in Ziphidium fasciatum, a long-horned grasshopper. In this material he recognized that an object thought by some to be a nucleolus was actually an unpaired chromosome. Although others had noticed that this object was distributed asymmetrically into some but not all spermatozoa, McClung was the first to see that this could provide a cytological mechanism of sex determination.

See Also:

D. H. Wenrich. 1946. Clarence Erwin McClung 1870-1946 Science, 103:551-552. DOI: 10.1126/science.103.2679.551

David Henry Wenrich Papers: A collection largely developed to support the Dr. Wenrich's efforts to honor Dr. Clarence Erwin McClung.

Walter S. Sutton (1877–1916)

Source: The Electronic Scholarly Publishing Project

Walter Stanborough Sutton was an American geneticist and physician whose most significant contribution to present-day biology was his theory that the Mendelian laws of inheritance could be applied to chromosomes at the cellular level of living organisms. This is now known as the Boveri-Sutton chromosome theory.

After graduating high school in Russell, he enrolled at the University of Kansas in engineering in 1896. Following the death of his younger brother (John) from typhus in 1897, Sutton switched his major to biology with an interest in medicine. While at the University of Kansas, both he and his older brother, William Sutton, played basketball for Dr. James Naismith. Sutton distinguished himself as student being elected to both Phi Beta Kappa and Sigma Xi and receiving both bachelor's and master's degrees by 1901. For his Masters thesis, he studied the spermatogenesis of Brachystola magna, a large grasshopper indigenous to the farmlands upon which Sutton was raised.

Considering the advice of his mentor at KU, Dr. C. E. McClung, Sutton moved to Columbia University for further study of zoology under Dr. Edmund B. Wilson. It was here that Sutton wrote his two significant works in genetics – “On the morphology of the chromosome group in Brachystola magna” and “The chromosomes in heredity”. The German biologist Theodor Boveri independently reached the same conclusions as Sutton, and their concepts are often referred to as the Boveri-Sutton chromosome theory. Sutton’s hypothesis was widely accepted by most scientists, particularly cytologists, at the time. The continued work of Thomas Hunt Morgan at Columbia brought the theory to universal acceptance by 1915 through his studies of Drosophila melanogaster, the fruit fly, even as William Bateson continued to question the theory until 1921. Sutton did not complete his PhD in Zoology as he originally planned. At the age of 26, he returned to the Kansas oil fields for 2 years. There he was able to perfect a device to start large gas engines with high pressure-gas and develop hoisting apparatuses for deep wells. Sutton’s mechanical aptitudes never left him. His father finally directed him to return to his medical studies and he did so returning to Columbia University in 1905. Sutton’s medical studies proceeded through the College of Physicians and Surgeons at Columbia University. While he continued to work on patents associated with oil drilling, Sutton also began at this stage to apply his mechanical aptitude to improving medical instruments. With credit for his graduate studies at both the University of Kansas and Columbia University, Sutton obtained his doctorate in medicine in 1907 graduating with “high standing”. He then began an internship at Roosevelt Hospital in New York working in the surgical division headed by Dr. Joseph Blake.

In 1909, Sutton returned to Kansas City, Kansas where his family had relocated and his father and brother were in law practice. Sutton was appointed assistant professor of surgery at the four-year-old University of Kansas Medical School. The tenuous nature of the appointment at the young school led him to also maintain a private practice and serve on the staff of St. Margaret’s Hospital as well as the University’s Bell Memorial Hospital. For six years, Sutton performed a wide range of surgeries carefully documenting the procedures. He published several articles related to these cases going back to his internship at Roosevelt. In 1911, he had accepted a commission as a First Lieutenant in the United States Army Medical reserve Corps. This eventually led to his taking a leave of absence from the University in February, 1915 to serve at the American Ambulance Hospital outside Paris. Sutton and others from his days at Columbia and Roosevelt arrived at College of Juilly on February 23 where hospital facilities had been set up only 40 miles from the front lines of World War I. Within 2 months, he was surgeon-in-chief handling administrative duties in addition to his surgical responsibilities. His inventive aptitude was perhaps never more valued as he developed fluoroscopic techniques to identify and localize shrapnel within the soldier’s bodies and then removed the foreign items with instruments of his own design. After his return, he documented these techniques in Binnie’s Manual of Operative Surgery.[11] Sutton’s return sailing from France was on June 26, 1915 having stayed only four months, but have made a significant contribution to wartime medical treatment. Dr. Sutton died rather unexpectedly at the age of 39 due to complications from acute appendicitis.

See Also:

Sutton, Walter S. 1902. On the morphology of the chromosome group in Brachystola magna. Biological Bulletin, 4:24-39.

Sutton, Walter S. 1903. The chromosomes in heredity. Biological Bulletin, 4: 231-251.

WIKIPEDIA: Walter Sutton

Crow, JF and Crow, EW 2002. 100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity. Genetics, 160:1-4.

The Embryo Project Encyclopedia: Walter Stansborough Sutton (1877–1916)

Hulston, Nancy Walter S. Sutton, MD: A Genius Goes To War

McKusick, Victor A. 1960. Walter S. Sutton and the Physical Basis of Mendelism. Bulletin of the History of Medicine, 34: 487.

Nettie Marie Stevens (1861–1912)

Source: Wikipedia

Nettie Maria Stevens was an early American geneticist. In 1906, she discovered that male beetles produce two kinds of sperm, one with a large chromosome and one with a small chromosome. When the sperm with the large chromosome fertilized eggs, they produced female offspring, and when the sperm with the small chromosome fertilized eggs, they produced male offspring. This pattern was observed in other animals, including humans, and became known as the XY sex-determination system.

See Also:

Smith, Kaitlin, "Nettie Maria Stevens (1861-1912)". Embryo Project Encyclopedia (2010-06-20). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/2028.

Reginald Crundall Punnett (1875–1967)

Source: Wikipedia

Reginald Crundall Punnett was a British geneticist who co-founded, with William Bateson, the Journal of Genetics in 1910. Punnett is probably best remembered today as the creator of the Punnett square, a tool still used by biologists to predict the probability of possible genotypes of offspring. His little book (62 small pages) Mendelism (1905) is sometimes said to have been the first textbook on genetics; it was probably the first popular science book to introduce genetics to the public.

Lucien Cuénot (1866–1951)

Source: Wikipedia

Lucien Claude Marie Julien Cuénot was a French biologist. In the first half of the 20th century, Mendelism was not a popular subject among French biologists. Cuénot defied popular opinion and shirked the “pseudo-sciences” as he called them. Upon the rediscovery of Mendel's work by Correns, De Vries, and Tschermak, Cuénot proved that Mendelism applied to animals as well as plants. Cuénot spent two years working on mice and came to the conclusion that three “mnemons” (genes) are responsible for the production of one “chromogen” or pigment and two “distases” enzymes. The pigment (if present) is acted upon by the enzymes to produce black or yellow colour. If no pigment is present the result is an albino mouse. Cuénot studied the offspring of various crosses between mice and concluded that these “mnemons” or genes were inherited in a Mendelian fashion. Subsequently, Cuénot was the first person to describe multiple allelism at a genetic locus. He also described a lethal mutation in the mouse agouti locus at a time when such a mutation was unheard of.

See Also:

Jean Gayon and Richard M. Burian. 2000. France in the Era of mendelism. Comptes rendus de l’Académie des Sciences, Paris. Sciences de la vie / Life Sciences, 323:1097-1106.

Godfrey Harold Hardy (1877–1947)

Source: Wikipedia

Godfrey Harold "G. H." Hardy was an English mathematician, known for his achievements in number theory and mathematical analysis. In addition to his research, Hardy is remembered for his 1940 essay on the aesthetics of mathematics, entitled A Mathematician's Apology. He was the mentor of the Indian mathematician Srinivasa Ramanujan.

Although every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and although nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics, most biologists don't realize that Hardy's total contribution to biology consisted of a single one-page letter to the editor in Science.

The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics. Mathematically, Hardy's "very simple point" was the trivial assertion that (p + q)² = p² + 2pq + q² Biologically, however, Hardy's point was of greater consequence, as his simple algebra implied that Mendelian mechanisms, acting alone, have no effect upon allele frequencies in a population — an observation that was far from obvious to most biologists.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Wilhelm Weinberg (1862–1937)

Source: Wikipedia

Dr Wilhelm Weinberg was a German obstetrician-gynecologist, practicing in Stuttgart, who in a 1908 paper, published in German in Jahresheft des Vereins für vaterländische Naturkunde in Württemberg (The Annals of the Society of National Natural History in Württemberg), expressed the concept that would later come to be known as the Hardy-Weinberg principle. Weinberg is also credited as the first to explain the effect of ascertainment bias on observations in genetics. Weinberg developed the principle of genetic equilibrium independently of British mathematician G.H. Hardy. He delivered an exposition of his ideas in a lecture on January 13, 1908, before the Verein für vaterländische Naturkunde in Württemberg (Society for the Natural History of the Fatherland in Württemberg), about six months before Hardy's paper was published in English. His lecture was printed later that year in the society's yearbook. Weinberg's contributions were unrecognized in the English speaking world for more than 35 years. Curt Stern, a German scientist who immigrated to the United States before World War II, pointed out in a brief paper in Science that Weinberg's exposition was both earlier and more comprehensive than Hardy's. Before 1943, the concepts in genetic equilibrium that are known today as the Hardy-Weinberg principle had been known as "Hardy's law" or "Hardy's formula" in English-language texts.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Calvin Blackman Bridges (1889–1938)

Source: Wikipedia

Calvin Blackman Bridges was born in Schuyler Falls, New York in 1889 to the parents of Leonard Bridges and Charlotte Blackman. Tragically, Calvin's mother died when he was two years old, and his father died a year after his mother's death, leaving Calvin Bridges an orphan. Following the death of his parents, Bridges was taken in and raised by his grandmother. Despite now being known in the scientific world as one of the most influential researchers regarding Drosophila melanogaster, it took Bridges several years to complete high school, graduating when he was 20 years old. However, despite this setback, Bridges moved on to be an outstanding student at Columbia University, which he attended both for undergraduate and postgraduate school. While taking a zoology class, Bridges met Thomas Hunt Morgan. This started a relationship which would lead to many important discoveries in the scientific world regarding genetics and evolution. Bridges wrote a masterful Ph.D. thesis on Non-disjunction as proof of the chromosome theory of heredity (click HERE for part 2 ) which appeared as the first paper in the first issue of the journal Genetics in 1916. In this paper, he also established that the Y-chromosome does not determine gender in Drosophila.

See Also:

Gleason, Kevin, "Calvin Blackman Bridges (1889-1938)". Embryo Project Encyclopedia (2017-05-19). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/11504.

Thomas Hunt Morgan (1866–1945)

Source: Wikipedia

Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Morgan received his Ph.D. from Johns Hopkins University in zoology in 1890 and researched embryology during his tenure at Bryn Mawr. Following the rediscovery of Mendelian inheritance in 1900, Morgan began to study the genetic characteristics of the fruit fly Drosophila melanogaster. In his famous Fly Room at Columbia University, Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of genetics. During his distinguished career, Morgan wrote 22 books and 370 scientific papers. As a result of his work, Drosophila became a major model organism in contemporary genetics. The Division of Biology which he established at the California Institute of Technology has produced seven Nobel Prize winners.

See Also:

Garland E. Allen. 1979. Thomas Hunt Morgan: The Man and His Science. Princeton: Princeton University Press. 447 pp. (The definitive biography)

Robert E. Kohler. 1994. Lords of the Fly: Drosophila Genetics and the Experimental Life. Chicago: University of Chicago Press. 344pp. (An excellent treatment of the early work in Drosophila genetics)

H. J. Muller. 1946. Thomas Hunt Morgan 1866–1945. Science, 103:550–551.

Diana E. Kenney and Gary G. Borisy. 2009. Thomas Hunt Morgan at the Marine Biological Laboratory: Naturalist and Experimentalist. Genetics, 181:841-846.

R. A. Fisher and G. R. de Beer. 1947. Thomas Hunt Morgan. 1866–1945. Obituary Notices of Fellows of the Royal Society, 5:451-466.

Stephen G. Brush. 2002. How Theories became Knowledge: Morgan's Chromosome Theory of Heredity in America and Britain. Journal of the History of Biology, 35:471–535.

Norman H. Horowitz. 1998. T. H. Morgan at Caltech: A Reminiscence. Genetics, 149:1629–1632.

Hermann Joseph Muller (1890–1967)

Source: Wikipedia

Hermann Joseph Muller (or H. J. Muller) was an American geneticist, educator, and Nobel laureate best known for his work on the physiological and genetic effects of radiation (Mutagenesis) as well as his outspoken political beliefs. Muller frequently warned of the long-term dangers of radioactive fallout from nuclear war and nuclear testing, helping to raise public awareness in this area. At 16 he entered Columbia College. From his first semester he was interested in biology; he became an early convert of the Mendelian-chromosome theory of heredity — and the concept of genetic mutations and natural selection as the basis for evolution. Muller remained at Columbia (the pre-eminent American zoology program at the time, thanks to E. B. Wilson and his students) for graduate school. He became interested in the Drosophila genetics work of Thomas Hunt Morgan's fly lab after undergraduate bottle washers Alfred Sturtevant and Calvin Bridges joined his Biology Club. He joined Morgan's group in 1912 (after two years of informal participation). In 1918, he proposed an explanation for the dramatic discontinuous alterations in Oenothera larmarckiana that were the basis of Hugo de Vries's theory of mutationism: "balanced lethals" allowed the accumulation of recessive mutations, and rare crossing over events resulted in the sudden expression of these hidden traits. In other words, de Vries's experiments were explainable by the Mendelian-chromosome theory.

Alfred Henry Sturtevant (1891–1970)

Source: Wikipedia

Alfred Henry Sturtevant was an American geneticist. While still a student, Sturtevant constructed the first genetic map of a chromosome in 1913. Throughout his career he worked on the organism Drosophila melanogaster with Thomas Hunt Morgan. By watching the development of flies in which the earliest cell division produced two different genomes, he measured the embryonic distance between organs in a unit which is called the sturt in his honor. In 1965, Sturtevant published a first-rate, first-person account of A History of Genetics.

See Also:

Edward B. Lewis. Alfred Henry Sturtevant November 21, 1891 – April 5, 1970. Biographical Memoirs of the National Academy of Science, 73:348–362.

Guide to the Alfred H. Sturtevant Papers, 1849-1969. Online Archive of California.

Thomas H. Montgomery, Jr. (1873–1912)

Source: Wikipedia

Thomas Harrison Montgomery Jr. was an American zoologist who made important contributions to cell biology–especially in chromosomes and their roles in sex determination–as well as the biology of birds and several groups invertebrates, naming many species of ribbon worms, rotifers, and spiders. He studied in Berlin before becoming a researcher and professor at the University of Pennsylvania, where he primarily worked until his death at the age of 39. In his short career he published 80 scientific papers and two books.

Harrison published 25 papers on cell biology, primarily using insect cells. His most notable research includes early observations of the pairing of maternal and paternal chromosomes during cell division. He was first to propose that chromosomes play the dominant role in sex determination, although he rejected the idea that sex was determined by chromosomes alone, and some historians claim he was the first to propose the chromosome theory of inheritance, an idea widely credited to Walter Sutton and Theodor Boveri. He also detailed the morphology of the nucleolus, and observed that in some hemipteran insects the germ cells of males but not females contain odd numbers of chromosomes, which is now known to influence sex-determination, A resolution of the American Society of Zoologists read after his death stated "it would be impossible to write a text-book upon the role of the chromosomes in the determination of sex without referring to his crucial labors in this field."

See Also:

Conklin, Edwin G. 1913. PROFESSOR THOMAS HARRISON MONTGOMERY, JR. Science, 38:207-214. DOI: 10.1126/science.38.972.207

Montgomery, Thos. H., Jr. 1910. ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS? Biological Bulletin, 19:1-17.

John Burton Sanderson Haldane (1892–1964)

Source: Wikipedia

John Burdon Sanderson Haldane was a British-born scientist known for his work in the study of physiology, genetics, evolutionary biology, and in mathematics, where he made innovative contributions to the fields of statistics and biostatistics. He was the son of the equally famous John Scott Haldane and was a professed socialist, Marxist, atheist, and humanist whose political dissent led him to leave England in 1956 and live in India, becoming a naturalised Indian citizen in 1961. His first paper in 1915 demonstrated genetic linkage in mammals while subsequent works helped to create population genetics, thus establishing a unification of Mendelian genetics and Darwinian evolution by natural selection whilst laying the groundwork for modern evolutionary synthesis.

He was one of the three major figures to develop the mathematical theory of population genetics, along with Ronald Fisher and Sewall Wright. Thusly he played an important role in the modern evolutionary synthesis, which is popularly called "neo-Darwinism", as in Richard Dawkins' 1976 work titled The Selfish Gene. He re-established natural selection as the premier mechanism of evolution by explaining it in terms of the mathematical consequences of Mendelian inheritance. He wrote a series of ten papers called A Mathematical Theory of Natural and Artificial Selection, on the numerical formalism underpinning natural selection. It showed that gene frequencies have direction and rates of change; and he pioneered the interaction of natural selection with mutation and animal migration. Haldane's book, The Causes of Evolution (1932), summarised these results, especially in its extensive appendix.

Arthur C. Clarke credited him as "perhaps the most brilliant science populariser of his generation". Nobel laureate Peter Medawar called Haldane "the cleverest man I ever knew".

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Frederick Twort (1877–1950)

Source: Wikipedia

Frederick William Twort was an English bacteriologist and was the original discoverer in 1915 of bacteriophages (viruses that infect bacteria). He studied medicine at St Thomas's Hospital, London, was superintendent of the Brown Institute for Animals (a pathology research centre), and was a professor of bacteriology at the University of London. He researched into Johne's disease, a chronic intestinal infection of cattle, and also discovered that vitamin K is needed by growing leprosy bacteria.

Early in the history of microbiology, bacteria were often differentiated testing their ability to grow on different media. Twort's first important paper found some shortcomings to this method. He found that the major subgroups identified by sugar fermentation were not capable of clear-cut subdivision by tests on glucosides, nor even were they strictly separable by sugars. Twort wrote, "It seems, therefore, probable that the separate micro-organisms in the various subgroups are not to be regarded as distinct species, but as varieties or hybrids of one or more species. If this be so, one might expect them to be constantly varying, losing old characters and gaining new ones according to the conditions under which they are grown, and it was with the object of testing this hypothesis that further series of experiments were undertaken." Following prolonged incubation in media that they previously failed to ferment, several species acquired fermentation powers which originally they did not enjoy. We now know that these mutant individuals able to ferment novel sugars arose in culture, and came to dominate the population. Although ignored at the time — a trend that seemed to plague his career — this work was quite prescient, and anticipated by decades the subsequent work on adaptation and mutation by bacterial chemists and microbiologists.

Twort and his brother, Dr. C. C. Twort, had for some years been trying to grow viruses in artificial media hoping to find a nonpathogenic virus, which might be the wild type of a pathogenic one, so more likely to grow. In 1914, Twort set out to identify the elusive (now known to be nonexistent) "essential substance" that would allow vaccinia virus to grow in vitro. At the time, smallpox vaccines had to be made in the skin of calves and was almost always contaminated with the bacterial genus Staphylococcus. Twort speculated the contaminating bacteria might be the source of the "essential substance" needed by vaccinia to survive. He plated some of the smallpox vaccines on nutrient agar slants and obtained large bacterial colonies of several colours. Upon closer examination of the colonies with a magnifying glass, he found minute glassy areas that would not grow when subcultured. He quickly realized these glassy areas were the result of the destruction of the bacterial cells and was able to pick from some of these areas and transmit this from one staphylococci colony to another.

Further experiments showed the agent could pass through porcelain filters and it required bacteria for growth. These observations show Twort had discovered most of the essential features of bacteriophages, although Twort seemed to favor the idea that the principle was not a separate form of life, but an enzyme which is secreted by the bacteria. Twort published these results in The Lancet in 1915 and called the contagion the bacteriolytic agent. Unfortunately, his discovery was ignored; Félix d'Herelle discovered phages independently, and Twort's work may have been lost to time, but for Jules Bordet and Andre Gratia's rediscovery of Twort's paper.

See Also:

Duckworth, D. H. 1976. "Who discovered bacteriophage?". Bacteriological Reviews. 40:793–802.

William E. Castle (1867–1962)

Source: Wikipedia

William Ernest Castle was born on a farm in Ohio and took an early interest in natural history. He graduated in 1889 from Denison University in Granville, Ohio, a Baptist college that emphasized classics, and went on to become a teacher of Latin at Ottawa University in Ottawa, Kansas, where he published his first paper on the flowering plants of the area. After three years of teaching, botany won out over Latin. Castle entered the senior class of Harvard University in 1892 and in 1893 took a second A.B. degree with honors. He was appointed laboratory assistant in zoology, an A.M. degree in 1894 and a Ph.D. in 1895. He then taught zoology at the University of Wisconsin–Madison and at the Knox College in Galesburg, Illinois, each for a year.

Castle returned to Harvard in 1897. His early work focused on embryology, but after the rediscovery of Mendelian genetics in 1900, he turned to mammalian genetics, especially that of the guinea pig. At Harvard, Charles W. Woodworth suggested to him that Drosophila might be used for genetical work. Castle was the first to use the fruit fly Drosophila melanogaster, and it was his work that inspired T. H. Morgan to use Drosophila and the basis of Morgan's 1933 Nobel Prize. In 1908 Castle moved from the Harvard Museum of Comparative Zoology to the Bussey Institution for Applied Biology. There his most famous PhD student was Sewall Wright who graduated in 1915. The same year he was elected to membership in the U.S. National Academy of Sciences. When the Eugenics Record Office was founded in 1912, he served as a member of its scientific advisory board, and in 1916 he was one of the 10 founders of the scientific journal Genetics.

See Also:

Dunn, L. C. 1965. William Ernest Castle 1867 – 1962. Biographical Memoirs, National Academy of Sciences.

Castle, W. E. 1911. Heredity in Relation to Evolution and Animal Breeding. New York: D. Appleton and Company. 184 pp.

William E. Castle Papers. American Philosophical Society.

Félix d'Herelle (1873–1949)

Source: Wikipedia

Félix d'Herelle was a French-Canadian microbiologist. He was co-discoverer of bacteriophages (viruses that infect bacteria) and experimented with the possibility of phage therapy. D'Herelle has also been credited for his contributions to the larger concept of applied microbiology.

In 1915, British bacteriologist Frederick W. Twort discovered a small agent that infects and kills bacteria, but did not pursue the issue further. Independently, the discovery of "an invisible, antagonistic microbe of the dysentery bacillus" by d'Herelle was announced on September 3, 1917. The isolation of phages by d'Herelle works like this: (1) Nutritional medium is infected with bacteria; the medium turns opaque; (2) The bacteria are infected with phages and die, producing new phages; the medium clears up; and (3) The medium is filtered through porcelain filter, holding back bacteria and larger objects; only the smaller phages pass through.

In early 1919, d'Herelle isolated phages from chicken feces, successfully treating a plague of chicken typhus with them. After this successful experiment on chicken, he felt ready for the first trial on humans. The first patient was healed of dysentery using phage therapy in August 1919. Many more followed. At the time, no one, not even d'Herelle, knew exactly what a phage was. D'Herelle claimed that it was a biological organism that reproduces, somehow feeding off bacteria. Others, the Nobelist Jules Bordet chief among them, theorized that phages were inanimate chemicals, enzymes specifically, that were already present in bacteria, and only trigger the release of similar proteins, killing the bacteria in the process. Due to this uncertainty, and d'Herelle using phages without much hesitation on humans, his work was under constant attack from many other scientists. It was not until the first phage was observed under an electron microscope by Helmut Ruska in 1939 that its true nature was established.

D'Herelle became widely known for his imaginative approaches to important problems in theoretical, as well as applied, microbiology. At the same time, he was widely reviled for his self-advertisement, his exaggerated claims of success and his sharp financial practices. He also had a talent for making enemies among powerful senior scientists. D'Herelle's main legacy lies in the use of phage in the molecular revolution in biology.

See Also:

Duckworth, D. H. 1976. "Who discovered bacteriophage?". Bacteriological Reviews. 40:793–802.

Ronald Aylmer Fisher (1890–1962)

Source: Wikipedia

Sir Ronald Aylmer Fisher, who published as R. A. Fisher, was an English statistician and biologist who used mathematics to combine Mendelian genetics and natural selection. This contributed to the revival of Darwinism in the early 20th century revision of the theory of evolution known as the modern synthesis. He was a prominent eugenicist in the early part of his life. In 1918 he published The Correlation Between Relatives on the Supposition of Mendelian Inheritance in 1918, in which he simultaneously resolved one of the outstanding debates in biology (the biometricians vs. the Mendelians) and introduced the idea of the analysis of variance. This paper was originally submitted to Biometrika where it was rejected, with a biological reviewer allowing that perhaps the mathematics had some value, but the biology was inconsequential while a statistical reviewer held the converse view. In 1925 he published Statistical Methods for Research Workers, one of the 20th century's most influential books on statistical methods. Fisher's method is a technique for data fusion or "meta-analysis" (analysis of analyses). This book also popularized the p-value, and it plays a central role in his approach. Fisher proposes the level p = 0.05, or a 1 in 20 chance of being exceeded by chance, as a limit for statistical significance, and applies this to a normal distribution (as a two-tailed test), thus yielding the rule of two standard deviations (on a normal distribution) for statistical significance. In 1933 he became Professor of Eugenics at University College London until 1939 when the department was dissolved. In 1935, he published by The Design of Experiments, which was also fundamental, [and promoted] statistical technique and application. In this book Fisher also outlined the Lady tasting tea, now a famous design of a statistical randomized experiment which uses Fisher's exact test and is the original exposition of Fisher's notion of a null hypothesis. In 1936 he published Has Mendel's Work Been Rediscovered?, in which he suggested that Mendel's results were too good to be true and that someone (perhaps an over-eager assistant) had fudged the results.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Sewall Wright (1889–1988)

Source: Wikipedia

Sewall Green Wright was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongside Ronald Fisher and J.B.S. Haldane, which was a major step in the development of the modern evolutionary synthesis combining genetics with evolution. He discovered the inbreeding coefficient and methods of computing it in pedigree animals. He extended this work to populations, computing the amount of inbreeding between members of populations as a result of random genetic drift, and along with Fisher he pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection, mutation, migration and genetic drift. Wright also made major contributions to mammalian and biochemical genetics. His papers on inbreeding, mating systems, and genetic drift make him a principal founder of theoretical population genetics, along with R. A. Fisher and J. B. S. Haldane. Their theoretical work is the origin of the modern evolutionary synthesis or neodarwinian synthesis. Wright was the inventor/discoverer of the inbreeding coefficient and F-statistics, standard tools in population genetics. He was the chief developer of the mathematical theory of genetic drift, which is sometimes known as the Sewall Wright effect, cumulative stochastic changes in gene frequencies that arise from random births, deaths, and Mendelian segregations in reproduction. In this work he also introduced the concept of effective population size. Wright was convinced that the interaction of genetic drift and the other evolutionary forces was important in the process of adaptation. He described the relationship between genotype or phenotype and fitness as fitness surfaces or evolutionary landscapes. On these landscapes mean population fitness was the height, plotted against horizontal axes representing the allele frequencies or the average phenotypes of the population. Natural selection would lead to a population climbing the nearest peak, while genetic drift would cause random wandering.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Frederick Griffith (1879–1941)

Source: Wikipedia

Frederick Griffith was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function. He showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. The observation was attributed to an unidentified transforming principle or transforming factor. This was later identified as DNA. America's leading pneumococcal researcher, Oswald T. Avery, speculated that Griffith had failed to apply adequate controls. A cautious and thorough researcher, and a reticent individual, Griffith's tendency was to publish only findings that he believed truly significant, and Griffith's findings were rapidly confirmed by researchers in Avery's laboratory. His discovery was one of the first to show the central role of DNA in heredity.

Griffith's experiment showed that one strain, R (rough, non-virulent) of bacteria could be transformed to exhibit the attributes of a different strain S (smooth, virulent),through exposure to material from dead members of the other strain. Specifically, he found that if he injected live R bacteria into mice, the mice lived (no surprise, R bacteria are non-virulent). He also found that if he injected deda S bacteria into mice, the mice lived (again, no surprise, dead bacteria do not cause disease). However, if he injected mice with a combination of live R and dead S, the mice died from an infection of live S bacteria. It appeared that exposure to dead S bacteria had transformed live R into live S bacteria.

This stunning result seemed to prove that there was some non-living, physical basis to bacteria hereditary — some molecular carrier of genetic information — that was being lost from the dead S bacteria and picked up by the live R bacteria, allowing the R to transform into S. Now the question became, What is the nature of that hereditary molecule?

In 1944, work by Oswald Avery, Colin MacLeod, and Maclyn McCarty, showed that DNA is the substance that causes bacterial transformation.

See Also:

Griffith's Experiment, Explained

The Avery–MacLeod–McCarty experiment

Theophilus S. Painter (1889–1969)

Source: Wikipedia

Theophilus Shickel Painter was an American zoologist best-known for his work on the structure and function of chromosomes, especially the sex-determination genes X and Y in humans. He also carried out work in identifying genes in fruit flies (Drosophila). His work exploited the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae. Painter joined the faculty at the University of Texas in 1916 and, except for military duty during World War I, stayed there his whole career. He was, in succession, associate professor, professor and distinguished professor of zoology. He served as acting president (1944–1946) and president (1946–1952) of the University of Texas and retired from active teaching in 1966.

Harriet Creighton (1909–2004)

Courtesy of Cold Spring Harbor Laboratory Archives. Noncommercial, educational use only.

Source: Wikipedia

Harriet Baldwin Creighton was an American botanist, geneticist and educator. Born in Delavan, Illinois, Creighton graduated from Wellesley College in 1929, and went on to complete her Ph.D. at Cornell University in 1933. During her time at Cornell she worked in the field of maize cytogenetics with Barbara McClintock, the pair published a very influential paper in 1931 in which they described chromosomal crossover for the first time. This paper, part of her Ph.D. research, provided key evidence that chromosomes carried and exchanged genetic information and hence that genes for physical traits are carried on chromosomes. Barbara McClintock guided her Ph.D. research. After completing her Ph.D. she taught at Cornell University and Connecticut College, and then returned to Wellesley where she taught until her retirement in 1974; taking time from her career to serve in the U.S. Navy during World War II.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Kass, Lee B. 2005c. Harriet B. Creighton: Proud botanist. Plant Science Bulletin. 51: 118-125. Available online, December 2005:

Barbara McClintock (1902–1992)

Source: Wikipedia

Barbara McClintock was an American scientist and cytogeneticist who was awarded the 1983 Nobel Prize in Physiology or Medicine. McClintock received her PhD in botany from Cornell University in 1927. There she started her career as the leader in the development of maize cytogenetics, the focus of her research for the rest of her life. From the late 1920s, McClintock studied chromosomes and how they change during reproduction in maize. She developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas. One of those ideas was the notion of genetic recombination by crossing-over during meiosis — a mechanism by which chromosomes exchange information. In 1930, McClintock was the first person to describe the cross-shaped interaction of homologous chromosomes during meiosis. The following year, McClintock and Creighton proved the link between chromosomal crossover during meiosis and the recombination of genetic traits. They observed how the recombination of chromosomes seen under a microscope correlated with new traits. Until this point, it had only been hypothesized that genetic recombination could occur during meiosis, although it had not been shown genetically. McClintock received a fellowship from the Guggenheim Foundation that made possible six months of training in Germany during 1933 and 1934. She had planned to work with Curt Stern, who had demonstrated crossing-over in Drosophila just weeks after McClintock and Creighton had done so; however, Stern emigrated to the United States. Instead, she worked with geneticist Richard B. Goldschmidt, who was the head of the Kaiser Wilhelm Institute. She left Germany early amidst mounting political tension in Europe, and returned to Cornell, remaining there until 1936, when she accepted an Assistant Professorship offered to her by Lewis Stadler in the Department of Botany at the University of Missouri-Columbia. She produced the first genetic map for maize, linking regions of the chromosome to physical traits. She demonstrated the role of the telomere and centromere, regions of the chromosome that are important in the conservation of genetic information. She was recognized among the best in the field, awarded prestigious fellowships, and elected a member of the National Academy of Sciences in 1944.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Barbara McClintock, DNA Learning Center

Milislav Demerec (1895–1966)

Source: Wikipedia

Milislav Demerec (January 11, 1895 – April 12, 1966) was a Croatian-American geneticist, and the director of the Department of Genetics, Carnegie Institution of Washington [CIW], now Cold Spring Harbor Laboratory (CSHL) from 1941 to 1960, recruiting Barbara McClintock and Alfred Hershey. Demerec was born and raised in Kostajnica (then Austria-Hungary, now Croatia). He attended College of Agriculture in Križevci, graduating in 1916. He worked at Križevci Experiment Station, and then attended the College of Agriculture in Grignon, France after World War I. He emigrated to the United States for graduate studies in 1919. In 1919 he started his PhD at Cornell University, his work was on maize genetics and was supervised by Rollins A. Emerson. He completed his PhD in 1923 and took up a research position at the Carnegie Institution of Washington's [CIW] Department of Genetics, now Cold Spring Harbor Laboratory. He completed work from his PhD, showing that ten different alleles could cause albinism in maize kernels, the at the advice of C. W. Metz he began work on the genetics of the plant Delphinium and the fruit fly Drosophila virilis studying mosaicism.

He became a prominent Drosophila researcher and established the Drosophila Information Service newsletter in 1934 with Calvin Bridges. In 1936 he was made the assistant directory of the Department of Genetics, and the acting director in 1941 following the retirement of Albert Blakeslee. That year, he was also made director of the Biological Laboratory of the Long Island Biological Association making him the director of both Cold Spring Harbor laboratories, by 1943.

After overcoming opposition from Thomas Hunt Morgan, Demerec oversaw the completion of much of the late Calvin Bridges’s work. Demerec appointed Katherine Brehme Warren to complete The Mutants of Drosophila melanogaster (1944) and the book became a classic in the field.

In the 1940s the direction of Demerec's research changed to the genetics of bacteria and their viruses after a symposium given by Max Delbrück. During World War II he used his knowledge of bacterial genetics to increase the yield from the Penicillium. Following the war he continued to work on bacterial genetics and the problem of antibiotic resistance in E. coli, Salmonella, and Staphylococcus. In 1946 he was elected to the National Academy of Sciences, and in 1947 became the founding editor of Advances in Genetics, the first journal to review the finding of modern genetics. In the 1950s he served on the genetics panel of the National Academy of Sciences' Committee on the Biological Effects of Atomic Radiation. In 1952 he was elected to the American Philosophical Society.

See Also:

Demerec, Milislav. 1933. What is a Gene? Journal of Heredity, 24:368-378.

Richard Goldschmidt (1878–1958)

Source: Wikipedia

Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony. Controversially, Goldschmidt advanced a model of macroevolution through macromutations that is popularly known as the "Hopeful Monster" hypothesis. Goldschmidt also described the nervous system of the nematode, a piece of work that later influenced Sydney Brenner to study the wiring diagram of Caenorhabditis elegans an achievement that later won Brenner and his colleagues the Nobel Prize in 2002.

In 1903 Goldschmidt began working as an assistant to Richard Hertwig at the University of Munich, where he continued his work on nematodes and their histology, including studies of the nervous system development of Ascaris and the anatomy of Amphioxus. He founded the histology journal Archiv für Zellforschung while working in Hertwig's laboratory. Under Hertwig's influence, he also began to take an interest in chromosome behavior and the new field of genetics. In 1909 Goldschmidt became professor at the University of Munich and, inspired by Wilhelm Johannsen's genetics treatise Elemente der exakten Erblichkeitslehre, began to study sex determination and other aspects of the genetics of the gypsy moth. His studies of the gypsy moth, which culminated in his 1934 monograph Lymantria, became the basis for his theory of sex determination, which he developed from 1911 until 1931. Goldschmidt left Munich in 1914 for the position as head of the genetics section of the newly founded Kaiser Wilhelm Institute for Biology. During a field trip to Japan in 1914 he was not able to return to Germany due to the outbreak of the First World War and got stranded in the United States. He ended up in an internment camp in Fort Oglethorpe, Georgia for "dangerous Germans". After his release in 1918 he returned to Germany in 1919 and worked at the Kaiser Wilhelm Institute. Sensing that it was unsafe for him to remain in Germany he emigrated to the United States 1936, where he became professor at the University of California, Berkeley. During World War 2, the Nazi party published a propaganda poster entitled "Jewish World Domination" displaying the Goldschmidt family tree.

Goldschmidt was the first scientist to use the term "hopeful monster". He thought that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution. In his book The Material Basis of Evolution (1940), he wrote "the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation." Goldschmidt believed the large changes in evolution were caused by macromutations (large mutations). His ideas about macromutations became known as the hopeful monster hypothesis, which is considered a type of saltational evolution. According to Goldschmidt, biologists seem inclined to think that because they have not themselves seen a 'large' mutation, such a thing cannot be possible. But such a mutation need only be an event of the most extraordinary rarity to provide the world with the important material for evolution. The origin of the first eukaryotic cell might be considered an example of a Goldschmidtian hopeful monster.

See Also:

Dietrich, Michael R. 2003. Richard Goldschmidt: hopeful monsters and other 'heresies'. Nature reviews Genetics, 4:68-74.

Boris Ephrussi (1901–1979)

Source: Wikipedia

Boris Ephrussi, Professor of Genetics at the University of Paris, was a Russo-French geneticist. Boris started his scientific training as a Russian émigré in 1920. He studied the initiation and regulation of embryological processes by intracellular and extracellular factors. A major strand of his early research concerned the effect of temperature on the development of fertilized sea urchin eggs. During Ephrussi's time, writing a second dissertation was standard practice in France. Ephrussi's involved culturing tissues. Ephrussi ran into difficulties typically associated with early tissue culture techniques, but despite these obstacles Ephrussi managed to conclude from studies of brachyury in mice that intrinsic factors (i.e. genes) play a key role in development.

As the next phase of his career, Ephrussi coupled his embryological concerns with a firm conviction that one must understand the role of genes in order to decipher embryological processes. He moved to Caltech in 1934 and stayed until 1935 to learn genetics within the intellectual empire of T.H. Morgan. This move was supported by the Rockefeller Foundation. During this period he conducted important work with George Beadle, who joined him in Paris in the autumn of 1935. There they produced results from experiments with Drosophila eye transplants. This became integral to the work of Beadle and Tatum, who were working with Neurospora, and from this research developed the one gene, one enzyme hypothesis.

See Also:

Chhetri, Divyash, "Beadle and Ephrussi's Transplantation Technique for Drosophila". Embryo Project Encyclopedia (2014-06-29). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/8015.

Theodosius Dobzhansky (1900–1975)

Source: Wikipedia

Theodosius Grygorovych Dobzhanskywas a prominent Russian-American geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the unifying modern evolutionary synthesis. Dobzhansky was born in Ukraine, then part of the Russian Empire, and became an immigrant to the United States in 1927, aged 27 years old. His 1937 work Genetics and the Origin of Species became a major influence on the synthesis and was awarded the US National Medal of Science in 1964, and the Franklin Medal in 1973.

Dobzhansky immigrated to the United States in 1927 on a scholarship from the International Education Board of the Rockefeller Foundation to work and study in the United States. Arriving in New York City on December 27, he worked with Thomas Hunt Morgan at Columbia University, who had pioneered the use of fruit flies (Drosophila melanogaster) in genetics experiments. He followed Morgan to the California Institute of Technology from 1930 to 1940. On the basis of his experiments, he articulated the idea that reproductive isolation can be caused by differences in presence of microbial symbionts between populations. In 1937, he published one of the major works of the modern evolutionary synthesis, the synthesis of evolutionary biology with genetics, entitled Genetics and the Origin of Species, which amongst other things, defined evolution as "a change in the frequency of an allele within a gene pool". Dobzhansky's work was instrumental in spreading the idea that it is through mutations in genes that natural selection takes place. Also in 1937, he became a naturalized citizen of the United States. During this time, he had a very public falling out with one of his Drosophila collaborators, Alfred Sturtevant, based primarily in professional competition.

Dobzhansky's wife Natasha died of coronary thrombosis on February 22, 1969. Earlier (on June 1, 1968) Theodosius had been diagnosed with lymphocytic leukemia (a chronic form of leukemia), and had been given a few months to a few years to live. He retired in 1971, moving to the University of California, Davis where his student Francisco Jose Ayala had been made assistant professor, and where he continued working as an emeritus professor. He published one of his most famous essays "Nothing in Biology Makes Sense Except in the Light of Evolution" at this time, influenced by the paleontologist/priest Pierre Teilhard de Chardin. By 1975, his leukemia had become more severe, and on November 11 he traveled to San Jacinto, California for treatment and care. He died (of heart failure) on December 18.

See Also:

Theodosius Dobzhansky. 1973. Nothing in Biology Makes Sense except in the Light of Evolution. The American Biology Teacher, 35:125-129.

Collected papers from a NAS colloquium on Dobzhansky's Genetics and the Origin of Species

Francisco J. Ayala. 1985. Theodosius Dobzhansky 1900 – 1975. Biographical Memoirs, National Academy of Sciences.

Theodosius Dobzhansky Papers. Americal Philosophical Society

Cyril Hinshelwood (1897–1967)

Source: Wikipedia

Sir Cyril Norman Hinshelwood was an English physical chemist and a Nobel Prize laureate. During the First World War, Hinshelwood was a chemist in an explosives factory. He was a tutor at Trinity College, Oxford from 1921 to 1937 and was Dr Lee's Professor of Chemistry at the University of Oxford from 1937. He served on several Advisory Councils on scientific matters to the British Government. His early studies of molecular kinetics led to the publication of Thermodynamics for Students of Chemistry and The Kinetics of Chemical Change in 1926. With Harold Warris Thompson he studied the explosive reaction of hydrogen and oxygen and described the phenomenon of chain reaction. His subsequent work on chemical changes in the bacterial cell proved to be of great importance in later research work on antibiotics and therapeutic agents, and his book, The Chemical Kinetics of the Bacterial Cell was published in 1946, followed by Growth, Function and Regulation in Bacterial Cells in 1966. In 1951 he published The Structure of Physical Chemistry. It was republished as an Oxford Classic Texts in the Physical Sciences by Oxford University Press in 2005.

Hinshelwood applied physical-chemistry thinking to bacteria and became convinced that bacteria possessed no true genetic apparatus and therefore exhibited no formal patterns of inheritance. He argued that apparent adaptive changes in bacterial populations (e.g., the emergence of antibiotic resistance) could be explained by a process involving shifts in stable chemical equilibria, induced by exposure to diufferent environmental conditions. He referred to this process as training.

This mistaken belief dominated thought about microbial genetics until Joshua Lederberg and Edward Tatum showed that genetic recombination can be detected among bacteria.

See Also:

The Nobel Prize in Chemistry 1956 was awarded jointly to Sir Cyril Norman Hinshelwood and Nikolay Nikolaevich Semenov for their researches into the mechanism of chemical reactions.

George Beadle (1903–1989)

Source: Wikipedia

George Wells Beadle was an American scientist in the field of genetics, and Nobel Prize in Physiology or Medicine Nobel laureate who with Edward Tatum discovered the role of genes in regulating biochemical events within cells in 1958. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. In 1931 Beadle was awarded a National Research Council Fellowship at the California Institute of Technology at Pasadena, where he remained from 1931 until 1936. During this period he continued his work on Indian corn and began, in collaboration with Professors Theodosius Dobzhansky, S. Emerson, and Alfred Sturtevant, work on crossing-over in the fruit fly, Drosophila melanogaster.

In 1935 Beadle visited Paris for six months to work with Professor Boris Ephrussi at the Institut de Biologie physico-chimique. Together they began the study of the development of eye pigment in Drosophila which later led to the work on the biochemistry of the genetics of the fungus Neurospora for which Beadle and Edward Lawrie Tatum were together awarded the 1958 Nobel Prize for Physiology or Medicine. In 1936 Beadle left the California Institute of Technology to become Assistant Professor of Genetics at Harvard University. A year later he was appointed Professor of Biology (Genetics) at Stanford University and there he remained for nine years, working for most of this period in collaboration with Tatum. In 1946 he returned to the California Institute of Technology as Professor of Biology and Chairman of the Division of Biology. Here he remained until January 1961 when he was elected Chancellor of the University of Chicago and, in the autumn of the same year, President of this University.

After retiring, Beadle undertook a remarkable experiment in maize genetics. In several laboratories he grew a series of Teosinte/Maize crosses. Then he crossed these progeny with each other. He looked for the rate of appearance of parent phenotypes among this second generation. The vast majority of these plants were intermediate between maize and Teosinte in their features, but about 1 in 500 of the plants were identical to either the parent maize or the parent teosinte. Using the mathematics of Mendelian genetics, he calculated that this showed a difference between maize and teosinte of about 5 or 6 genetic loci. This demonstration was so compelling that most scientists now agree that Teosinte is the wild progenitor of maize.

See Also:

Norman H. Horowitz. 1990. George Wells Beadle 1903 – 1989. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, "George W. Beadle's One Gene-One Enzyme Hypothesis". Embryo Project Encyclopedia (2014-05-23). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7892.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Salvador Luria (1912–1991)

Source: Wikipedia

Salvador Edward Luria was an Italian microbiologist, later a naturalized U.S. citizen. He won the Nobel Prize in Physiology or Medicine in 1969, with Max Delbrück and Alfred Hershey, for their discoveries on the replication mechanism and the genetic structure of viruses. Salvador Luria also showed that bacterial resistance to viruses (phages) is genetically inherited. Luria was born Salvatore Edoardo Luria, in Turin, Italy to an influential Italian Sephardi Jewish family. His parents were Ester (Sacerdote) and Davide Luria. He attended the medical school at the University of Turin studying with Giuseppe Levi. There, he met two other future Nobel laureates: Rita Levi-Montalcini and Renato Dulbecco. He graduated from the University of Turin in 1935. From 1936 to 1937, Luria served his required time in the Italian army as a medical officer. He then took classes in radiology at the University of Rome. Here, he was introduced to Max Delbrück's theories on the gene as a molecule and began to formulate methods for testing genetic theory with the bacteriophages, viruses that infect bacteria. In 1938, he received a fellowship to study in the United States, where he intended to work with Delbrück. Soon after Luria received the award, Benito Mussolini's fascist regime banned Jews from academic research fellowships. Without funding sources for work in the U.S. or Italy, Luria left his home country for Paris, France in 1938. As the Nazi German armies invaded France in 1940, Luria fled on bicycle to Marseille where he received an immigration visa to the United States.

Luria arrived in New York City on September 12, 1940, and soon changed his first and middle names. With the help of physicist Enrico Fermi, whom he knew from his time at the University of Rome, Luria received a Rockefeller Foundation fellowship at Columbia University. He soon met Delbrück and Hershey, and they collaborated on experiments at Cold Spring Harbor Laboratory and in Delbrück's lab at Vanderbilt University. His famous experiment with Delbrück in 1943, known as the Luria–Delbrück experiment, demonstrated statistically that inheritance in bacteria must follow Darwinian rather than Lamarckian principles and that mutant bacteria occurring randomly can still bestow viral resistance without the virus being present. The idea that natural selection affects bacteria has profound consequences, for example, it explains how bacteria develop antibiotic resistance. From 1943 to 1950, he worked at Indiana University. His first graduate student was James D. Watson, who went on to discover the structure of DNA with Francis Crick. In January 1947, Luria became a naturalized citizen of the United States.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Julian Huxley (1887–1975)

Source: Wikipedia

Sir Julian Sorell Huxley was a British evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern evolutionary synthesis. He was secretary of the Zoological Society of London (1935–1942), the first Director of UNESCO, a founding member of the World Wildlife Fund and the first President of the British Humanist Association. Huxley came from the distinguished Huxley family. His brother was the writer Aldous Huxley, and his half-brother a fellow biologist and Nobel laureate, Andrew Huxley; his father was writer and editor Leonard Huxley; and his paternal grandfather was Thomas Henry Huxley, a friend and supporter of Charles Darwin and proponent of evolution. His maternal grandfather was the academic Tom Arnold, his great-uncle was poet Matthew Arnold and his great-grandfather was Thomas Arnold of Rugby School.

Huxley was one of the main architects of the modern evolutionary synthesis which took place around the time of World War II. The synthesis of genetic and population ideas produced a consensus which reigned in biology from about 1940, and which is still broadly tenable. His book Evolution: The Modern Synthesis was written while he was secretary to the Zoological Society, and made use of his remarkable collection of reprints covering the first part of the century. It was published in 1942. Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing". Huxley's main co-respondents in the modern evolutionary synthesis are usually listed as Ernst Mayr, Theodosius Dobzhansky, George Gaylord Simpson, Bernhard Rensch, Ledyard Stebbins and the population geneticists J. B. S. Haldane, Ronald Fisher and Sewall Wright.

Despite its ecstatic initial reception, the limits of Huxley's Modern Synthesis are now becoming more obvious. A particular problem is the book's completely inadequate treatment of microbial genetics:

Bacteria ... appear to be not only wholly asexual but premitotic. Their hereditary constitution is not differentiated into specialized parts with different functions. They have no genes in the sense of accurately quantized portions of hereditary substance; and therefore they have no need for the accurate division of the genetic system which is accomplished by mitosis. ... That occasional 'mutations' occur we know, but there is no ground for supposing that they are similar in nature to those of higher organisms, nor, since they are usually reversible according to conditions, that they play the same part in evolution. We must, in fact, expect that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms. J. Huxley, 1943, Evolution: The Modern Synthesis, New York: Harper & Brothers Publishers, pp. 131–132.

Although it is now clear that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms, this is not because bacteria possess no genes in the sense of accurately quantized portions of hereditary substance.

Max Delbrück (1906–1981)

Source: Wikipedia

Max Ludwig Henning Delbrück, a German–American biophysicist, helped launch the molecular biology research program in the late 1930s. He stimulated physical scientists' interest into biology, especially as to basic research to physically explain genes, mysterious at the time. Formed in 1945 and led by Delbrück along with Salvador Luria and Alfred Hershey, the Phage Group made substantial headway unraveling important aspects of genetics. The three shared the 1969 Nobel Prize in Physiology or Medicine "for their discoveries concerning the replication mechanism and the genetic structure of viruses". He was the first physicist to predict what is now called Delbrück scattering. Delbrück was born in Berlin, German Empire. His mother was granddaughter of Justus von Liebig, eminent chemist, while his father Hans Delbrück was a history professor at the University of Berlin. In 1937, Max left Nazi Germany for America—first California, then Tennessee—becoming a US citizen in 1945.

In 1937, he attained a fellowship from Rockefeller Foundation—which was launching the molecular biology research program—to research genetics of the fruit fly, Drosophila melanogaster, in California Institute of Technology's biology department, where Delbrück could blend interests in biochemistry and genetics. While at Caltech, Delbrück researched bacteria and their viruses (bacteriophages or phages). In 1939, with E.L. Ellis, he coauthored "The growth of bacteriophage", a paper reporting that the viruses reproduce in one step, not exponentially as do cellular organisms. Although Delbrück's Rockefeller Foundation fellowship expired in 1939, the Foundation matched him up with Vanderbilt University in Nashville, Tennessee, where from 1940 to 1947 he taught physics, yet had his laboratory in the biology department. In 1941, Delbrück met Salvador Luria of Indiana University who began visiting Vanderbilt. In 1942, Delbrück and Luria published on bacterial resistance to virus infection mediated by random mutation. Alfred Hershey of Washington University began visiting in 1943. The Luria–Delbrück experiment, also called the Fluctuation Test, demonstrated that Darwin's theory of natural selection acting on random mutations applies to bacteria as well as to more complex organisms. The 1969 Nobel Prize in Physiology or Medicine was awarded to both scientists in part for this work.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Erwin Schrödinger (1887–1961)

Source: Wikipedia

Erwin Rudolf Josef Alexander Schrödinger, was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in the field of quantum theory, which formed the basis of wave mechanics: he formulated the wave equation (stationary and time-dependent Schrödinger equation) and revealed the identity of his development of the formalism and matrix mechanics. Schrödinger proposed an original interpretation of the physical meaning of the wave function. In addition, he was the author of many works in various fields of physics: statistical mechanics and thermodynamics, physics of dielectrics, colour theory, electrodynamics, general relativity, and cosmology, and he made several attempts to construct a unified field theory. In his 1944 book What Is Life? Schrödinger addressed the problems of genetics, looking at the phenomenon of life from the point of view of physics.

In the book, Schrödinger introduced the paradoxical idea of an aperiodic crystal that contained genetic information in its configuration of covalent chemical bonds. [The idea of an aperiodic crystal bears a passing resemblance to the notion of dehydrated water.] In the book, Schrödinger specifically discussed the likelihood that hereditary information is somehow encoded in the molecular structure of chromosomes, noting:

It is these chromosomes, or probably only an axial skeleton fibre of what we actually see under the microscope as the chromosome, that contain in some kind of code-script the entire pattern of the individual's future development and of its functioning in the mature state. Every complete set of chromosomes contains the full code; so there are, as a rule, two copies of the latter in the fertilized egg cell, which forms the earliest stage of the future individual. In calling the structure of the chromosome fibres a code-script we mean that the all-penetrating mind, once conceived by Laplace, to which every causal connection lay immediately open, could tell from their structure whether the egg would develop, under suitable conditions, into a black cock or into a speckled hen, into a fly or a maize plant, a rhododendron, a beetle, a mouse or a woman.

In retrospect, Schrödinger's aperiodic crystal can be viewed as a well-reasoned theoretical prediction of what biologists should have been looking for during their search for genetic material. Both James D. Watson, and independently, Francis Crick, co-discoverers of the structure of DNA, credited Schrödinger's book with presenting an early theoretical description of how the storage of genetic information would work, and each respectively acknowledged the book as a source of inspiration for their initial researches. These ideas provide the conceptual foundation of molecular genetics. Schrödinger paid great attention to the philosophical aspects of science, ancient and oriental philosophical concepts, ethics, and religion. He also wrote on philosophy and theoretical biology. He is also known for his Schrödinger's cat thought-experiment.

Oswald Avery Jr. (1877–1955)

Source: Wikipedia

Oswald Theodore Avery Jr. was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller University Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment (published in 1944 with his co-workers Colin MacLeod and Maclyn McCarty) that isolated DNA as the material of which genes and chromosomes are made. For many years, genetic information was thought to be contained in cell protein. Continuing the research done by Frederick Griffith in 1927, Avery worked with MacLeod and McCarty on the mystery of inheritance. He had received emeritus status from the Rockefeller Institute in 1943, but continued working for five years, though by that time he was in his late sixties. Techniques were available to remove various organic compounds from bacteria, and if the remaining organic compounds were still able to cause R strain bacteria to transform then the substances removed could not be the carrier of genes. S-strain bacteria first had the large cellular structures removed. Then they were treated with protease enzymes, which removed the proteins from the cells before the remainder was placed with R strain bacteria. The R strain bacteria transformed, meaning that proteins did not carry the genes causing the disease. Then the remnants of the R strain bacteria were treated with a deoxyribonuclease enzyme which removed the DNA. After this treatment, the R strain bacteria no longer transformed. This indicated that DNA was the carrier of genes in cells.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Colin Munro MacLeod (1909–1972)

Source: Wikipedia

Colin Munro MacLeod was a Canadian-American geneticist. He was one of a trio of scientists who discovered that deoxyribonucleic acid, or DNA is responsible for the transformation of the physical characteristics of bacteria, which subsequently led to its identification as the molecule responsible for heredity. In his early years as a research scientist, MacLeod, with Oswald Avery and Maclyn McCarty, demonstrated DNA is the molecule responsible for bacterial transformation — and in retrospect, the physical basis of the gene. In 1941, Avery and MacLeod separated a crude extract from smooth (S) strains of Streptococcus pneumoniae, the most common cause of bacterial pneumonia. The S strain extract could convert the more benign rough (R) strains of pneumococci into the disease-causing S form. Later that year, McCarty joined the Avery laboratory, and in 1942, the group began to focus on DNA as the elusive ingredient in the S strain extract as the factor responsible for transformation of R pneumococci into S pneumococci. By early 1943, Avery, MacLeod, and McCarty had shown that DNA was the transforming factor, and in February 1944, published the first of a series of scientific papers in the Journal of Experimental Medicine demonstrating that DNA was the transforming principle. Subsequent experiments confirmed DNA as a universal bearer of genetic information. However, despite the enormous scientific importance of this work, which became known as the Avery–MacLeod–McCarty experiment, the trio did not win a Nobel Prize for their discovery.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Walsh McDermott. 1983. Colin Munro MacLeod, 1909–1972. Biographical Memoirs, National Academy of Sciences.

Maclyn McCarty (1911–2005)

Source: Wikipedia

Maclyn McCarty, who devoted his life as a physician-scientist to studying infectious disease organisms, was best known for his part in the monumental discovery that DNA, rather than protein, constituted the chemical nature of a gene. Uncovering the molecular secret of the gene in question — that for the capsular polysaccharide of pneumococcal bacteria — led the way to studying heredity not only through genetics but also through chemistry, and initiated the dawn of the age of molecular biology. McCarty was the youngest and longest surviving member of the research team responsible for this feat (known as the Avery–MacLeod–McCarty experiment), which also included Oswald T. Avery and Colin MacLeod; he died on January 2, 2005, from congestive heart failure. McCarty was born in 1911 in South Bend, Indiana, the second of four sons of a branch manager for the Studebaker Corporation while it was still a firm for horse-drawn carriages. In his teens, McCarty set himself the goal of becoming a physician-scientist, and he pursued a successful strategy to prepare for admission to, and early success in, Johns Hopkins University Medical School. As an undergraduate at Stanford University, he presciently began his studies in the nascent field of biochemistry, working with James Murray Luck on protein turnover in the liver. In 1937, he began his clinical training in pediatrics at the Harriet Lane Service at Johns Hopkins University. There McCarty developed a special interest in infectious diseases — in particular, antibacterial sulfonamide drug treatments that were just entering medicine — which he subsequently pursued by moving to New York University to work with William Tillett. A National Research Council Fellowship in the medical sciences and an opening in Oswald T. Avery's laboratory spurred his move to Rockefeller University in 1941. At that time, research in the Avery laboratory was focused on the pneumococcal transformation, the heritable alteration of a pneumococcal strain from a nonvirulent rough form to a virulent smooth encapsulated form. McCarty's arrival at the Rockefeller Institute in September 1941 marked 13 years since this discovery, also known as the Griffith phenomenon.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Lederberg, Joshua, and Gotschlich, Emil C. 2005. A Path to Discovery: The Career of Maclyn McCarty. PLoS Biology, 3:e341.

Joshua Lederberg (1925–2008)

Source: Wikipedia

Joshua Lederberg was an American molecular biologist known for his work in microbial genetics, artificial intelligence, and the United States space program. He was 33 years old when he won the 1958 Nobel Prize in Physiology or Medicine for discovering that bacteria can mate and exchange genes (bacterial conjugation). He shared the prize with Edward Tatum and George Beadle, who won for their work with genetics. He enrolled in Columbia University in 1941, majoring in zoology. Under the mentorship of Francis J. Ryan, he conducted biochemical and genetic studies on the bread mold Neurospora crassa. Intending to receive his MD and fulfill his military service obligations, Lederberg worked as a hospital corpsman during 1943 in the clinical pathology laboratory at St. Albans Naval Hospital, where he examined sailors' blood and stool samples for malaria. He went on to receive his undergraduate degree in 1944.

Joshua Lederberg began medical studies at Columbia's College of Physicians and Surgeons while continuing to perform experiments. Inspired by Oswald Avery's discovery of the importance of DNA, Lederberg began to investigate his hypothesis that, contrary to prevailing opinion, bacteria did not simply pass down exact copies of genetic information, making all cells in a lineage essentially clones. After making little progress at Columbia, Lederberg wrote to Edward Tatum, Ryan's post-doctoral mentor, proposing a collaboration. In 1946 and 1947, Lederberg took a leave of absence to study under the mentorship of Tatum at Yale University. Lederberg and Tatum showed that the bacterium Escherichia coli entered a sexual phase during which it could share genetic information through bacterial conjugation. With this discovery and some mapping of the E. coli chromosome, Lederberg was able to receive his Ph.D. from Yale University in 1947. Instead of returning to Columbia to finish his medical degree, Lederberg chose to accept an offer of an assistant professorship in genetics at the University of Wisconsin–Madison. In 1951, Lederberg and Norton Zinder showed that genetic material could be transferred from one strain of the bacterium Salmonella typhimurium to another using viral material as an intermediary step. This process is called transduction.

In 1958, Joshua Lederberg received the Nobel Prize and moved to Stanford University, where he was the founder and chairman of the Department of Genetics. In 1978, he became the president of Rockefeller University, until he stepped down in 1990 and became professor-emeritus of molecular genetics and informatics at Rockefeller University, considering his extensive research and publications in these disciplines. Throughout his career, Lederberg was active as a scientific advisor to the U.S. government.

See Also:

Walter Bodmer and Ann Ganesan. 2011. Joshua Lederberg. 23 May 1925 – 2 February 2008. Biographical Memoirs of Fellows of the Royal Society. 57: 229–251. doi:10.1098/rsbm.2010.0024

Joshua Lederberg Papers 1904-2008

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

S. Gaylen Bradley. 2009. Joshua Lederberg 1925 – 2008. National Academy of Sciences, Biographical Memoirs

Edward Tatum (1909–1975)

Source: Wikipedia

Edward Lawrie Tatum was an American geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Beadle for showing that genes control individual steps in metabolism. The other half of that year's award went to Joshua Lederberg. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments, published in 1941, led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. This became a fundamental concept in physiological genetics. Tatum went on to study genetics in bacteria. An active area of research in his laboratory was to understand the basis of Tryptophan biosynthesis in Escherichia coli. Later, Tatum and his student Joshua Lederberg showed that E. coli could share genetic information through recombination. This became a fundamental concept in microbial genetics.

See Also:

Joshua Lederberg. 1990. Edward Lawrie Tatum 1909 – 1975. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Ching Chun Li (1912–2003)

Source: Wikipedia

Ching Chun Li was a respected American population geneticist and human geneticist. Li was best known for his book An Introduction to Population Genetics and his teaching in human genetics. Ching Chun Li was born on October 27, 1912, in Taku, Tianjin, China. He received his BS degree in agronomy from the University of Nanking in 1936 and a PhD in plant breeding and genetics from Cornell University in 1940. He worked as post-doctorate fellows at Columbia University and North Carolina State University from 1940 to 1941. Li returned to China at the age of 30 and became the Professor of Genetics and Biometry at University of Nanking, his alma mater, in 1943. After World War II, he moved to Beijing for a Professorship of Agronomy at Peking University in 1946, where he finished An Introduction to Population Genetics in 1948. The book was the first notable publication where the population-genetics ideas of Ronald Fisher, Sewall Wright, and J. B. S. Haldane were brought together, synthesized, and presented in a coherent and readily understood manner.

See Also:

Aravinda Chakravarti. 2004. Ching Chun Li (1912–2003): A Personal Remembrance of a Hero of Genetics. The American Journal of Human Genetics, 74:789-792.

Eliot B. Spiess. 2005. Remembrance of Ching Chun Li, 1912–2003. Genetics, 169:9-11.

Erwin Chargaff (1905–2002)

Source: Wikipedia

Erwin Chargaff (11 August 1905 – 20 June 2002) was an Austro-Hungarian biochemist that immigrated to the United States during the Nazi era and was a professor of biochemistry at Columbia University medical school. Through careful experimentation, Chargaff made two observations that helped to disprove the tetranucleotide model of DNA. Under the tetranucleotide hypothesis, it was assumed that DNA was built as a simple repeating polymer of units consisting of one adenine, one thymine, one cytosine, and one guanine. Such a structure would mean that all DNA molecules has essentially the same structure, differeing only in length. Such a molecule would be incapable of carrying hereditary information. Chargaff's observations: (1) the percent nucleotide composition of DNA was not exactly 25% of each nucleotide, (2) the percent nucleotide composition of DNA differed (slightly) from one species to another, and (3) the percent nucleotide composition of DNA was constant within a species. He also observed regular numerical patterns in the nucleotide makeup of any DNA sample. The two best remembered patterns are that, in any DNA sample, the amount of adenine always equals the amount of thymine, and the amount of guanine always equals the amount of cytosine. These observations, especially the A-T and C-G equalities, helped Watson and Crick devise the double-helix model of DNA. Chargaff had a quick wit and a sharp pen and he was not impressed with advances made through theory rather than through laboratory work. He once commented that Molecular biology is essentially the practice of biochemistry without a license.

James Dewey Watson (1928–      )

Source: Wikipedia

James Dewey Watson is an American molecular biologist, geneticist and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick. Watson, Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". From 1956 to 1976, Watson was on the faculty of the Harvard University Biology Department, promoting research in molecular biology. From 1968 he served as director of Cold Spring Harbor Laboratory (CSHL), greatly expanding its level of funding and research. At CSHL, he shifted his research emphasis to the study of cancer, along with making it a world leading research center in molecular biology. In 1994, he started as president and served for 10 years. He was then appointed chancellor, serving until he resigned in 2007. Between 1988 and 1992, Watson was associated with the National Institutes of Health, helping to establish the Human Genome Project.

Francis Crick (1916–2004)

Source: Wikipedia

Francis Harry Compton Crick was a British molecular biologist, biophysicist, and neuroscientist, most noted for being a co-discoverer of the structure of the DNA molecule in 1953 with James Watson. Together with Watson and Maurice Wilkins, he was jointly awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". Crick was an important theoretical molecular biologist and played a crucial role in research related to revealing the helical structure of DNA. He is widely known for use of the term "central dogma" to summarize the idea that genetic information flow in cells is essentially one-way, from DNA to RNA to protein. During the remainder of his career, he held the post of J.W. Kieckhefer Distinguished Research Professor at the Salk Institute for Biological Studies in La Jolla, California. His later research centered on theoretical neurobiology and attempts to advance the scientific study of human consciousness. He remained in this post until his death; "he was editing a manuscript on his death bed, a scientist until the bitter end" according to Christof Koch.

Gregor Mendel (1822–1884)

Source: Wikipedia

Gregor Johann Mendel was a scientist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire (today's Czech Republic) and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance.

See Also:

Vítězslav Orel. 1996. Gregor Mendel: The First Geneticist. Oxford: Oxford University Press. 376 pp.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — a facsimile of the original publication in German.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — translated into English.

Mendel's paper, "Experiments on Plant Hybridization" (German: Versuche über Pflanzen-Hybriden) — translated into English, with sidenote annotations.

Robin Marantz Henig. 2001. The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics. New York: Mariner Books. 304 pp.

Simon Mawer. 2006. Gregor Mendel: Planting the Seeds of Genetics. Harry N Abrams. 176pp.

Andrei, Amanda, ""Experiments in Plant Hybridization" (1866), by Johann Gregor Mendel". Embryo Project Encyclopedia (2013-09-04). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/6240.

Edmund Beecher Wilson (1856–1939)

Source: Wikipedia

Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell in Development and Inheritance. He and Nettie Maria Stevens were the first researchers to describe the chromosomal basis of sex, but they conducted their research independently of each other. Wilson is credited as America's first cell biologist. In 1898 he used the similarity in embryos to describe phylogenetic relationships. By observing spiral cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells and concluded that all these organisms must have a common ancestor.

William Bateson (1861–1926)

Source: Wikipedia

William Bateson was an English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscovery in 1900 by Hugo de Vries and Carl Correns. Bateson first suggested using the word "genetics" to describe the study of inheritance and the science of variation in a personal letter to Adam Sedgwick who had been Darwin's professor), dated 18 April 1905. Bateson first used the term "genetics" publicly at the Third International Conference on Plant Hybridization in London in 1906.

Erich von Tschermak (1864–1933)

Source: Wikipedia

Erich Tschermak, Edler von Seysenegg was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gustav Tschermak von Seysenegg. His maternal grandfather was the famous botanist, Eduard Fenzl, who taught Gregor Mendel botany during his student days in Vienna.

Carl Correns (1864–1933)

Source: Wikipedia

Carl Erich Correns was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, and for his rediscovery of Gregor Mendel's earlier paper on that subject, which he achieved simultaneously but independently of the botanists Erich Tschermak von Seysenegg and Hugo de Vries, and the agronomist William Jasper Spillman. Carl Correns conducted much of the foundational work for the field of genetics at the turn of the 20th century. He rediscovered and independently verified the work of Mendel in a separate model organism. He also discovered cytoplasmic inheritance, an important extension of Mendel's theories, which demonstrated the existence of extra-chromosomal factors on phenotype. Most of Correns' work went unpublished however, and was destroyed in the Berlin bombings of 1945.

Hugo de Vries (1848–1935)

Source: Wikipedia

Hugo Marie de Vries was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution. In 1889, De Vries published his book Intracellular Pangenesis, in which, based on a modified version of Charles Darwin's theory of Pangenesis of 1868, he postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles. He called these units pangenes, a term 20 years later to be shortened to genes by Wilhelm Johannsen.

See Also:

Ralph E. Cleland. 1936. Hugo de Vries. Proceedings of the American Philosophical Society, 76:248-250.

Theodor Boveri (1862–1915)

Source: Embryo Project

Theodor Heinrich Boveri was a German biologist. He was notable for first hypothesising the cellular processes that cause cancer. Boveri's work with sea urchins showed that it was necessary to have all chromosomes present in order for proper embryonic development to take place. This discovery was an important part of the Boveri–Sutton chromosome theory, which identifies chromosomes as the carriers of genetic material. The theory correctly explains the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors (particles) required by Mendel's laws. The chromosome theory of inheritance is credited to papers by Walter Sutton in 1902 and 1903, as well as to independent work by Theodor Boveri during roughly the same period. Boveri's thoughts are summarized in his book Ergebnisse über die Konstitution der chromatischen Substanz des Zellkerns (Results on the constitution of the chromatic substance of the cell nucleus), Jena: Verlag von Gustav Fischer, 1904. His other significant discovery was the centrosome (1888), which he described as the especial organ of cell division. Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode Parascaris.

Archibald Garrod (1857–1938)

Source: Wikipedia

Sir Archibald Edward Garrod was an English physician who pioneered the field of inborn errors of metabolism. He also discovered alkaptonuria, understanding its inheritance. He served as Regius Professor of Medicine at the University of Oxford from 1920 to 1927. Garrod is best known for his scientific study of inborn errors of metabolism. He developed an increasing interest in chemical pathology, and investigated urine chemistry as a reflection of systemic metabolism and disease. This research, combined with the new understanding of Mendelian inheritance, evolved from an investigation of a few families with an obscure and not very dangerous disease (alkaptonuria) to the realization that a whole territory of mysterious diseases might be understood as inherited disorders of metabolism. Working with William Bateson, Garrod came to understand the pattern of alkaptonuria appearance in children based on Mendelian principles. Once he applied Mendel’s concepts to alkaptonuria, he published a paper in 1902 called The Incidence of Alkaptonuria: A Study of Chemical Individuality. In the paper, Garrod explains how he came to understand the condition and speculates as to its causes. He cites various case studies and compares alkaptonuria to albinism in how it is inherited. He summarized his thoughts on the relationship of inheritance to metabolic disease in his book Inborn Errors of Metabolism .

See Also:

F. G. Hopkins. 1938. Archibald Edward Garrod. 1857–1936. Biographical Memoirs of fellows of the Royal Society, 2:225–228.

Krishna Dronamraju. 1992. BIOGRAPHY Profiles in Genetics: Archibald E. Garrod (1857-1936). american Journal of Human Genetics, 51:216-219.

Clarence Erwin McClung (1870–1946)

Source: Wikipedia

Clarence Erwin (CE) McClung was an American zoologist of wide-ranging interests. Although born in California, he spent much of his early life in Kansas. He originally studied pharmacy at Kansas University, receiving the Ph.G. degree in 1892. He taught pharmacy at the University for a year, but then his interest shifted to more general biological questions and he reenrolled as a student. From Kansas University he received the A.B. degree in 1896, the A.M. in 1898, and the Ph.D. in 1902. CE McClung made important contributions to early genetics, but he was also a general zoologist and paleontologist who received all of his degrees from Kansas and then spent his early career on the faculty there, ultimately assuming the positions of chair of the zoology department, curator of vertebrate paleontology, and even acting dean of the medical school. Early in his career, he undertook an investigation of spermatogenesis in Ziphidium fasciatum, a long-horned grasshopper. In this material he recognized that an object thought by some to be a nucleolus was actually an unpaired chromosome. Although others had noticed that this object was distributed asymmetrically into some but not all spermatozoa, McClung was the first to see that this could provide a cytological mechanism of sex determination.

See Also:

D. H. Wenrich. 1946. Clarence Erwin McClung 1870-1946 Science, 103:551-552. DOI: 10.1126/science.103.2679.551

David Henry Wenrich Papers: A collection largely developed to support the Dr. Wenrich's efforts to honor Dr. Clarence Erwin McClung.

Walter S. Sutton (1877–1916)

Source: The Electronic Scholarly Publishing Project

Walter Stanborough Sutton was an American geneticist and physician whose most significant contribution to present-day biology was his theory that the Mendelian laws of inheritance could be applied to chromosomes at the cellular level of living organisms. This is now known as the Boveri-Sutton chromosome theory.

After graduating high school in Russell, he enrolled at the University of Kansas in engineering in 1896. Following the death of his younger brother (John) from typhus in 1897, Sutton switched his major to biology with an interest in medicine. While at the University of Kansas, both he and his older brother, William Sutton, played basketball for Dr. James Naismith. Sutton distinguished himself as student being elected to both Phi Beta Kappa and Sigma Xi and receiving both bachelor's and master's degrees by 1901. For his Masters thesis, he studied the spermatogenesis of Brachystola magna, a large grasshopper indigenous to the farmlands upon which Sutton was raised.

Considering the advice of his mentor at KU, Dr. C. E. McClung, Sutton moved to Columbia University for further study of zoology under Dr. Edmund B. Wilson. It was here that Sutton wrote his two significant works in genetics – “On the morphology of the chromosome group in Brachystola magna” and “The chromosomes in heredity”. The German biologist Theodor Boveri independently reached the same conclusions as Sutton, and their concepts are often referred to as the Boveri-Sutton chromosome theory. Sutton’s hypothesis was widely accepted by most scientists, particularly cytologists, at the time. The continued work of Thomas Hunt Morgan at Columbia brought the theory to universal acceptance by 1915 through his studies of Drosophila melanogaster, the fruit fly, even as William Bateson continued to question the theory until 1921. Sutton did not complete his PhD in Zoology as he originally planned. At the age of 26, he returned to the Kansas oil fields for 2 years. There he was able to perfect a device to start large gas engines with high pressure-gas and develop hoisting apparatuses for deep wells. Sutton’s mechanical aptitudes never left him. His father finally directed him to return to his medical studies and he did so returning to Columbia University in 1905. Sutton’s medical studies proceeded through the College of Physicians and Surgeons at Columbia University. While he continued to work on patents associated with oil drilling, Sutton also began at this stage to apply his mechanical aptitude to improving medical instruments. With credit for his graduate studies at both the University of Kansas and Columbia University, Sutton obtained his doctorate in medicine in 1907 graduating with “high standing”. He then began an internship at Roosevelt Hospital in New York working in the surgical division headed by Dr. Joseph Blake.

In 1909, Sutton returned to Kansas City, Kansas where his family had relocated and his father and brother were in law practice. Sutton was appointed assistant professor of surgery at the four-year-old University of Kansas Medical School. The tenuous nature of the appointment at the young school led him to also maintain a private practice and serve on the staff of St. Margaret’s Hospital as well as the University’s Bell Memorial Hospital. For six years, Sutton performed a wide range of surgeries carefully documenting the procedures. He published several articles related to these cases going back to his internship at Roosevelt. In 1911, he had accepted a commission as a First Lieutenant in the United States Army Medical reserve Corps. This eventually led to his taking a leave of absence from the University in February, 1915 to serve at the American Ambulance Hospital outside Paris. Sutton and others from his days at Columbia and Roosevelt arrived at College of Juilly on February 23 where hospital facilities had been set up only 40 miles from the front lines of World War I. Within 2 months, he was surgeon-in-chief handling administrative duties in addition to his surgical responsibilities. His inventive aptitude was perhaps never more valued as he developed fluoroscopic techniques to identify and localize shrapnel within the soldier’s bodies and then removed the foreign items with instruments of his own design. After his return, he documented these techniques in Binnie’s Manual of Operative Surgery.[11] Sutton’s return sailing from France was on June 26, 1915 having stayed only four months, but have made a significant contribution to wartime medical treatment. Dr. Sutton died rather unexpectedly at the age of 39 due to complications from acute appendicitis.

See Also:

Sutton, Walter S. 1902. On the morphology of the chromosome group in Brachystola magna. Biological Bulletin, 4:24-39.

Sutton, Walter S. 1903. The chromosomes in heredity. Biological Bulletin, 4: 231-251.

WIKIPEDIA: Walter Sutton

Crow, JF and Crow, EW 2002. 100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity. Genetics, 160:1-4.

The Embryo Project Encyclopedia: Walter Stansborough Sutton (1877–1916)

Hulston, Nancy Walter S. Sutton, MD: A Genius Goes To War

McKusick, Victor A. 1960. Walter S. Sutton and the Physical Basis of Mendelism. Bulletin of the History of Medicine, 34: 487.

Nettie Marie Stevens (1861–1912)

Source: Wikipedia

Nettie Maria Stevens was an early American geneticist. In 1906, she discovered that male beetles produce two kinds of sperm, one with a large chromosome and one with a small chromosome. When the sperm with the large chromosome fertilized eggs, they produced female offspring, and when the sperm with the small chromosome fertilized eggs, they produced male offspring. This pattern was observed in other animals, including humans, and became known as the XY sex-determination system.

See Also:

Smith, Kaitlin, "Nettie Maria Stevens (1861-1912)". Embryo Project Encyclopedia (2010-06-20). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/2028.

Reginald Crundall Punnett (1875–1967)

Source: Wikipedia

Reginald Crundall Punnett was a British geneticist who co-founded, with William Bateson, the Journal of Genetics in 1910. Punnett is probably best remembered today as the creator of the Punnett square, a tool still used by biologists to predict the probability of possible genotypes of offspring. His little book (62 small pages) Mendelism (1905) is sometimes said to have been the first textbook on genetics; it was probably the first popular science book to introduce genetics to the public.

Lucien Cuénot (1866–1951)

Source: Wikipedia

Lucien Claude Marie Julien Cuénot was a French biologist. In the first half of the 20th century, Mendelism was not a popular subject among French biologists. Cuénot defied popular opinion and shirked the “pseudo-sciences” as he called them. Upon the rediscovery of Mendel's work by Correns, De Vries, and Tschermak, Cuénot proved that Mendelism applied to animals as well as plants. Cuénot spent two years working on mice and came to the conclusion that three “mnemons” (genes) are responsible for the production of one “chromogen” or pigment and two “distases” enzymes. The pigment (if present) is acted upon by the enzymes to produce black or yellow colour. If no pigment is present the result is an albino mouse. Cuénot studied the offspring of various crosses between mice and concluded that these “mnemons” or genes were inherited in a Mendelian fashion. Subsequently, Cuénot was the first person to describe multiple allelism at a genetic locus. He also described a lethal mutation in the mouse agouti locus at a time when such a mutation was unheard of.

See Also:

Jean Gayon and Richard M. Burian. 2000. France in the Era of mendelism. Comptes rendus de l’Académie des Sciences, Paris. Sciences de la vie / Life Sciences, 323:1097-1106.

Godfrey Harold Hardy (1877–1947)

Source: Wikipedia

Godfrey Harold "G. H." Hardy was an English mathematician, known for his achievements in number theory and mathematical analysis. In addition to his research, Hardy is remembered for his 1940 essay on the aesthetics of mathematics, entitled A Mathematician's Apology. He was the mentor of the Indian mathematician Srinivasa Ramanujan.

Although every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and although nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics, most biologists don't realize that Hardy's total contribution to biology consisted of a single one-page letter to the editor in Science.

The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics. Mathematically, Hardy's "very simple point" was the trivial assertion that (p + q)² = p² + 2pq + q² Biologically, however, Hardy's point was of greater consequence, as his simple algebra implied that Mendelian mechanisms, acting alone, have no effect upon allele frequencies in a population — an observation that was far from obvious to most biologists.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Wilhelm Weinberg (1862–1937)

Source: Wikipedia

Dr Wilhelm Weinberg was a German obstetrician-gynecologist, practicing in Stuttgart, who in a 1908 paper, published in German in Jahresheft des Vereins für vaterländische Naturkunde in Württemberg (The Annals of the Society of National Natural History in Württemberg), expressed the concept that would later come to be known as the Hardy-Weinberg principle. Weinberg is also credited as the first to explain the effect of ascertainment bias on observations in genetics. Weinberg developed the principle of genetic equilibrium independently of British mathematician G.H. Hardy. He delivered an exposition of his ideas in a lecture on January 13, 1908, before the Verein für vaterländische Naturkunde in Württemberg (Society for the Natural History of the Fatherland in Württemberg), about six months before Hardy's paper was published in English. His lecture was printed later that year in the society's yearbook. Weinberg's contributions were unrecognized in the English speaking world for more than 35 years. Curt Stern, a German scientist who immigrated to the United States before World War II, pointed out in a brief paper in Science that Weinberg's exposition was both earlier and more comprehensive than Hardy's. Before 1943, the concepts in genetic equilibrium that are known today as the Hardy-Weinberg principle had been known as "Hardy's law" or "Hardy's formula" in English-language texts.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Calvin Blackman Bridges (1889–1938)

Source: Wikipedia

Calvin Blackman Bridges was born in Schuyler Falls, New York in 1889 to the parents of Leonard Bridges and Charlotte Blackman. Tragically, Calvin's mother died when he was two years old, and his father died a year after his mother's death, leaving Calvin Bridges an orphan. Following the death of his parents, Bridges was taken in and raised by his grandmother. Despite now being known in the scientific world as one of the most influential researchers regarding Drosophila melanogaster, it took Bridges several years to complete high school, graduating when he was 20 years old. However, despite this setback, Bridges moved on to be an outstanding student at Columbia University, which he attended both for undergraduate and postgraduate school. While taking a zoology class, Bridges met Thomas Hunt Morgan. This started a relationship which would lead to many important discoveries in the scientific world regarding genetics and evolution. Bridges wrote a masterful Ph.D. thesis on Non-disjunction as proof of the chromosome theory of heredity (click HERE for part 2 ) which appeared as the first paper in the first issue of the journal Genetics in 1916. In this paper, he also established that the Y-chromosome does not determine gender in Drosophila.

See Also:

Gleason, Kevin, "Calvin Blackman Bridges (1889-1938)". Embryo Project Encyclopedia (2017-05-19). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/11504.

Thomas Hunt Morgan (1866–1945)

Source: Wikipedia

Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Morgan received his Ph.D. from Johns Hopkins University in zoology in 1890 and researched embryology during his tenure at Bryn Mawr. Following the rediscovery of Mendelian inheritance in 1900, Morgan began to study the genetic characteristics of the fruit fly Drosophila melanogaster. In his famous Fly Room at Columbia University, Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of genetics. During his distinguished career, Morgan wrote 22 books and 370 scientific papers. As a result of his work, Drosophila became a major model organism in contemporary genetics. The Division of Biology which he established at the California Institute of Technology has produced seven Nobel Prize winners.

See Also:

Garland E. Allen. 1979. Thomas Hunt Morgan: The Man and His Science. Princeton: Princeton University Press. 447 pp. (The definitive biography)

Robert E. Kohler. 1994. Lords of the Fly: Drosophila Genetics and the Experimental Life. Chicago: University of Chicago Press. 344pp. (An excellent treatment of the early work in Drosophila genetics)

H. J. Muller. 1946. Thomas Hunt Morgan 1866–1945. Science, 103:550–551.

Diana E. Kenney and Gary G. Borisy. 2009. Thomas Hunt Morgan at the Marine Biological Laboratory: Naturalist and Experimentalist. Genetics, 181:841-846.

R. A. Fisher and G. R. de Beer. 1947. Thomas Hunt Morgan. 1866–1945. Obituary Notices of Fellows of the Royal Society, 5:451-466.

Stephen G. Brush. 2002. How Theories became Knowledge: Morgan's Chromosome Theory of Heredity in America and Britain. Journal of the History of Biology, 35:471–535.

Norman H. Horowitz. 1998. T. H. Morgan at Caltech: A Reminiscence. Genetics, 149:1629–1632.

Hermann Joseph Muller (1890–1967)

Source: Wikipedia

Hermann Joseph Muller (or H. J. Muller) was an American geneticist, educator, and Nobel laureate best known for his work on the physiological and genetic effects of radiation (Mutagenesis) as well as his outspoken political beliefs. Muller frequently warned of the long-term dangers of radioactive fallout from nuclear war and nuclear testing, helping to raise public awareness in this area. At 16 he entered Columbia College. From his first semester he was interested in biology; he became an early convert of the Mendelian-chromosome theory of heredity — and the concept of genetic mutations and natural selection as the basis for evolution. Muller remained at Columbia (the pre-eminent American zoology program at the time, thanks to E. B. Wilson and his students) for graduate school. He became interested in the Drosophila genetics work of Thomas Hunt Morgan's fly lab after undergraduate bottle washers Alfred Sturtevant and Calvin Bridges joined his Biology Club. He joined Morgan's group in 1912 (after two years of informal participation). In 1918, he proposed an explanation for the dramatic discontinuous alterations in Oenothera larmarckiana that were the basis of Hugo de Vries's theory of mutationism: "balanced lethals" allowed the accumulation of recessive mutations, and rare crossing over events resulted in the sudden expression of these hidden traits. In other words, de Vries's experiments were explainable by the Mendelian-chromosome theory.

Alfred Henry Sturtevant (1891–1970)

Source: Wikipedia

Alfred Henry Sturtevant was an American geneticist. While still a student, Sturtevant constructed the first genetic map of a chromosome in 1913. Throughout his career he worked on the organism Drosophila melanogaster with Thomas Hunt Morgan. By watching the development of flies in which the earliest cell division produced two different genomes, he measured the embryonic distance between organs in a unit which is called the sturt in his honor. In 1965, Sturtevant published a first-rate, first-person account of A History of Genetics.

See Also:

Edward B. Lewis. Alfred Henry Sturtevant November 21, 1891 – April 5, 1970. Biographical Memoirs of the National Academy of Science, 73:348–362.

Guide to the Alfred H. Sturtevant Papers, 1849-1969. Online Archive of California.

Thomas H. Montgomery, Jr. (1873–1912)

Source: Wikipedia

Thomas Harrison Montgomery Jr. was an American zoologist who made important contributions to cell biology–especially in chromosomes and their roles in sex determination–as well as the biology of birds and several groups invertebrates, naming many species of ribbon worms, rotifers, and spiders. He studied in Berlin before becoming a researcher and professor at the University of Pennsylvania, where he primarily worked until his death at the age of 39. In his short career he published 80 scientific papers and two books.

Harrison published 25 papers on cell biology, primarily using insect cells. His most notable research includes early observations of the pairing of maternal and paternal chromosomes during cell division. He was first to propose that chromosomes play the dominant role in sex determination, although he rejected the idea that sex was determined by chromosomes alone, and some historians claim he was the first to propose the chromosome theory of inheritance, an idea widely credited to Walter Sutton and Theodor Boveri. He also detailed the morphology of the nucleolus, and observed that in some hemipteran insects the germ cells of males but not females contain odd numbers of chromosomes, which is now known to influence sex-determination, A resolution of the American Society of Zoologists read after his death stated "it would be impossible to write a text-book upon the role of the chromosomes in the determination of sex without referring to his crucial labors in this field."

See Also:

Conklin, Edwin G. 1913. PROFESSOR THOMAS HARRISON MONTGOMERY, JR. Science, 38:207-214. DOI: 10.1126/science.38.972.207

Montgomery, Thos. H., Jr. 1910. ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS? Biological Bulletin, 19:1-17.

John Burton Sanderson Haldane (1892–1964)

Source: Wikipedia

John Burdon Sanderson Haldane was a British-born scientist known for his work in the study of physiology, genetics, evolutionary biology, and in mathematics, where he made innovative contributions to the fields of statistics and biostatistics. He was the son of the equally famous John Scott Haldane and was a professed socialist, Marxist, atheist, and humanist whose political dissent led him to leave England in 1956 and live in India, becoming a naturalised Indian citizen in 1961. His first paper in 1915 demonstrated genetic linkage in mammals while subsequent works helped to create population genetics, thus establishing a unification of Mendelian genetics and Darwinian evolution by natural selection whilst laying the groundwork for modern evolutionary synthesis.

He was one of the three major figures to develop the mathematical theory of population genetics, along with Ronald Fisher and Sewall Wright. Thusly he played an important role in the modern evolutionary synthesis, which is popularly called "neo-Darwinism", as in Richard Dawkins' 1976 work titled The Selfish Gene. He re-established natural selection as the premier mechanism of evolution by explaining it in terms of the mathematical consequences of Mendelian inheritance. He wrote a series of ten papers called A Mathematical Theory of Natural and Artificial Selection, on the numerical formalism underpinning natural selection. It showed that gene frequencies have direction and rates of change; and he pioneered the interaction of natural selection with mutation and animal migration. Haldane's book, The Causes of Evolution (1932), summarised these results, especially in its extensive appendix.

Arthur C. Clarke credited him as "perhaps the most brilliant science populariser of his generation". Nobel laureate Peter Medawar called Haldane "the cleverest man I ever knew".

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

William E. Castle (1867–1962)

Source: Wikipedia

William Ernest Castle was born on a farm in Ohio and took an early interest in natural history. He graduated in 1889 from Denison University in Granville, Ohio, a Baptist college that emphasized classics, and went on to become a teacher of Latin at Ottawa University in Ottawa, Kansas, where he published his first paper on the flowering plants of the area. After three years of teaching, botany won out over Latin. Castle entered the senior class of Harvard University in 1892 and in 1893 took a second A.B. degree with honors. He was appointed laboratory assistant in zoology, an A.M. degree in 1894 and a Ph.D. in 1895. He then taught zoology at the University of Wisconsin–Madison and at the Knox College in Galesburg, Illinois, each for a year.

Castle returned to Harvard in 1897. His early work focused on embryology, but after the rediscovery of Mendelian genetics in 1900, he turned to mammalian genetics, especially that of the guinea pig. At Harvard, Charles W. Woodworth suggested to him that Drosophila might be used for genetical work. Castle was the first to use the fruit fly Drosophila melanogaster, and it was his work that inspired T. H. Morgan to use Drosophila and the basis of Morgan's 1933 Nobel Prize. In 1908 Castle moved from the Harvard Museum of Comparative Zoology to the Bussey Institution for Applied Biology. There his most famous PhD student was Sewall Wright who graduated in 1915. The same year he was elected to membership in the U.S. National Academy of Sciences. When the Eugenics Record Office was founded in 1912, he served as a member of its scientific advisory board, and in 1916 he was one of the 10 founders of the scientific journal Genetics.

See Also:

Dunn, L. C. 1965. William Ernest Castle 1867 – 1962. Biographical Memoirs, National Academy of Sciences.

Castle, W. E. 1911. Heredity in Relation to Evolution and Animal Breeding. New York: D. Appleton and Company. 184 pp.

William E. Castle Papers. American Philosophical Society.

Ronald Aylmer Fisher (1890–1962)

Source: Wikipedia

Sir Ronald Aylmer Fisher, who published as R. A. Fisher, was an English statistician and biologist who used mathematics to combine Mendelian genetics and natural selection. This contributed to the revival of Darwinism in the early 20th century revision of the theory of evolution known as the modern synthesis. He was a prominent eugenicist in the early part of his life. In 1918 he published The Correlation Between Relatives on the Supposition of Mendelian Inheritance in 1918, in which he simultaneously resolved one of the outstanding debates in biology (the biometricians vs. the Mendelians) and introduced the idea of the analysis of variance. This paper was originally submitted to Biometrika where it was rejected, with a biological reviewer allowing that perhaps the mathematics had some value, but the biology was inconsequential while a statistical reviewer held the converse view. In 1925 he published Statistical Methods for Research Workers, one of the 20th century's most influential books on statistical methods. Fisher's method is a technique for data fusion or "meta-analysis" (analysis of analyses). This book also popularized the p-value, and it plays a central role in his approach. Fisher proposes the level p = 0.05, or a 1 in 20 chance of being exceeded by chance, as a limit for statistical significance, and applies this to a normal distribution (as a two-tailed test), thus yielding the rule of two standard deviations (on a normal distribution) for statistical significance. In 1933 he became Professor of Eugenics at University College London until 1939 when the department was dissolved. In 1935, he published by The Design of Experiments, which was also fundamental, [and promoted] statistical technique and application. In this book Fisher also outlined the Lady tasting tea, now a famous design of a statistical randomized experiment which uses Fisher's exact test and is the original exposition of Fisher's notion of a null hypothesis. In 1936 he published Has Mendel's Work Been Rediscovered?, in which he suggested that Mendel's results were too good to be true and that someone (perhaps an over-eager assistant) had fudged the results.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Sewall Wright (1889–1988)

Source: Wikipedia

Sewall Green Wright was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongside Ronald Fisher and J.B.S. Haldane, which was a major step in the development of the modern evolutionary synthesis combining genetics with evolution. He discovered the inbreeding coefficient and methods of computing it in pedigree animals. He extended this work to populations, computing the amount of inbreeding between members of populations as a result of random genetic drift, and along with Fisher he pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection, mutation, migration and genetic drift. Wright also made major contributions to mammalian and biochemical genetics. His papers on inbreeding, mating systems, and genetic drift make him a principal founder of theoretical population genetics, along with R. A. Fisher and J. B. S. Haldane. Their theoretical work is the origin of the modern evolutionary synthesis or neodarwinian synthesis. Wright was the inventor/discoverer of the inbreeding coefficient and F-statistics, standard tools in population genetics. He was the chief developer of the mathematical theory of genetic drift, which is sometimes known as the Sewall Wright effect, cumulative stochastic changes in gene frequencies that arise from random births, deaths, and Mendelian segregations in reproduction. In this work he also introduced the concept of effective population size. Wright was convinced that the interaction of genetic drift and the other evolutionary forces was important in the process of adaptation. He described the relationship between genotype or phenotype and fitness as fitness surfaces or evolutionary landscapes. On these landscapes mean population fitness was the height, plotted against horizontal axes representing the allele frequencies or the average phenotypes of the population. Natural selection would lead to a population climbing the nearest peak, while genetic drift would cause random wandering.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Theophilus S. Painter (1889–1969)

Source: Wikipedia

Theophilus Shickel Painter was an American zoologist best-known for his work on the structure and function of chromosomes, especially the sex-determination genes X and Y in humans. He also carried out work in identifying genes in fruit flies (Drosophila). His work exploited the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae. Painter joined the faculty at the University of Texas in 1916 and, except for military duty during World War I, stayed there his whole career. He was, in succession, associate professor, professor and distinguished professor of zoology. He served as acting president (1944–1946) and president (1946–1952) of the University of Texas and retired from active teaching in 1966.

Harriet Creighton (1909–2004)

Courtesy of Cold Spring Harbor Laboratory Archives. Noncommercial, educational use only.

Source: Wikipedia

Harriet Baldwin Creighton was an American botanist, geneticist and educator. Born in Delavan, Illinois, Creighton graduated from Wellesley College in 1929, and went on to complete her Ph.D. at Cornell University in 1933. During her time at Cornell she worked in the field of maize cytogenetics with Barbara McClintock, the pair published a very influential paper in 1931 in which they described chromosomal crossover for the first time. This paper, part of her Ph.D. research, provided key evidence that chromosomes carried and exchanged genetic information and hence that genes for physical traits are carried on chromosomes. Barbara McClintock guided her Ph.D. research. After completing her Ph.D. she taught at Cornell University and Connecticut College, and then returned to Wellesley where she taught until her retirement in 1974; taking time from her career to serve in the U.S. Navy during World War II.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Kass, Lee B. 2005c. Harriet B. Creighton: Proud botanist. Plant Science Bulletin. 51: 118-125. Available online, December 2005:

Barbara McClintock (1902–1992)

Source: Wikipedia

Barbara McClintock was an American scientist and cytogeneticist who was awarded the 1983 Nobel Prize in Physiology or Medicine. McClintock received her PhD in botany from Cornell University in 1927. There she started her career as the leader in the development of maize cytogenetics, the focus of her research for the rest of her life. From the late 1920s, McClintock studied chromosomes and how they change during reproduction in maize. She developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas. One of those ideas was the notion of genetic recombination by crossing-over during meiosis — a mechanism by which chromosomes exchange information. In 1930, McClintock was the first person to describe the cross-shaped interaction of homologous chromosomes during meiosis. The following year, McClintock and Creighton proved the link between chromosomal crossover during meiosis and the recombination of genetic traits. They observed how the recombination of chromosomes seen under a microscope correlated with new traits. Until this point, it had only been hypothesized that genetic recombination could occur during meiosis, although it had not been shown genetically. McClintock received a fellowship from the Guggenheim Foundation that made possible six months of training in Germany during 1933 and 1934. She had planned to work with Curt Stern, who had demonstrated crossing-over in Drosophila just weeks after McClintock and Creighton had done so; however, Stern emigrated to the United States. Instead, she worked with geneticist Richard B. Goldschmidt, who was the head of the Kaiser Wilhelm Institute. She left Germany early amidst mounting political tension in Europe, and returned to Cornell, remaining there until 1936, when she accepted an Assistant Professorship offered to her by Lewis Stadler in the Department of Botany at the University of Missouri-Columbia. She produced the first genetic map for maize, linking regions of the chromosome to physical traits. She demonstrated the role of the telomere and centromere, regions of the chromosome that are important in the conservation of genetic information. She was recognized among the best in the field, awarded prestigious fellowships, and elected a member of the National Academy of Sciences in 1944.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Barbara McClintock, DNA Learning Center

Milislav Demerec (1895–1966)

Source: Wikipedia

Milislav Demerec (January 11, 1895 – April 12, 1966) was a Croatian-American geneticist, and the director of the Department of Genetics, Carnegie Institution of Washington [CIW], now Cold Spring Harbor Laboratory (CSHL) from 1941 to 1960, recruiting Barbara McClintock and Alfred Hershey. Demerec was born and raised in Kostajnica (then Austria-Hungary, now Croatia). He attended College of Agriculture in Križevci, graduating in 1916. He worked at Križevci Experiment Station, and then attended the College of Agriculture in Grignon, France after World War I. He emigrated to the United States for graduate studies in 1919. In 1919 he started his PhD at Cornell University, his work was on maize genetics and was supervised by Rollins A. Emerson. He completed his PhD in 1923 and took up a research position at the Carnegie Institution of Washington's [CIW] Department of Genetics, now Cold Spring Harbor Laboratory. He completed work from his PhD, showing that ten different alleles could cause albinism in maize kernels, the at the advice of C. W. Metz he began work on the genetics of the plant Delphinium and the fruit fly Drosophila virilis studying mosaicism.

He became a prominent Drosophila researcher and established the Drosophila Information Service newsletter in 1934 with Calvin Bridges. In 1936 he was made the assistant directory of the Department of Genetics, and the acting director in 1941 following the retirement of Albert Blakeslee. That year, he was also made director of the Biological Laboratory of the Long Island Biological Association making him the director of both Cold Spring Harbor laboratories, by 1943.

After overcoming opposition from Thomas Hunt Morgan, Demerec oversaw the completion of much of the late Calvin Bridges’s work. Demerec appointed Katherine Brehme Warren to complete The Mutants of Drosophila melanogaster (1944) and the book became a classic in the field.

In the 1940s the direction of Demerec's research changed to the genetics of bacteria and their viruses after a symposium given by Max Delbrück. During World War II he used his knowledge of bacterial genetics to increase the yield from the Penicillium. Following the war he continued to work on bacterial genetics and the problem of antibiotic resistance in E. coli, Salmonella, and Staphylococcus. In 1946 he was elected to the National Academy of Sciences, and in 1947 became the founding editor of Advances in Genetics, the first journal to review the finding of modern genetics. In the 1950s he served on the genetics panel of the National Academy of Sciences' Committee on the Biological Effects of Atomic Radiation. In 1952 he was elected to the American Philosophical Society.

See Also:

Demerec, Milislav. 1933. What is a Gene? Journal of Heredity, 24:368-378.

Richard Goldschmidt (1878–1958)

Source: Wikipedia

Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony. Controversially, Goldschmidt advanced a model of macroevolution through macromutations that is popularly known as the "Hopeful Monster" hypothesis. Goldschmidt also described the nervous system of the nematode, a piece of work that later influenced Sydney Brenner to study the wiring diagram of Caenorhabditis elegans an achievement that later won Brenner and his colleagues the Nobel Prize in 2002.

In 1903 Goldschmidt began working as an assistant to Richard Hertwig at the University of Munich, where he continued his work on nematodes and their histology, including studies of the nervous system development of Ascaris and the anatomy of Amphioxus. He founded the histology journal Archiv für Zellforschung while working in Hertwig's laboratory. Under Hertwig's influence, he also began to take an interest in chromosome behavior and the new field of genetics. In 1909 Goldschmidt became professor at the University of Munich and, inspired by Wilhelm Johannsen's genetics treatise Elemente der exakten Erblichkeitslehre, began to study sex determination and other aspects of the genetics of the gypsy moth. His studies of the gypsy moth, which culminated in his 1934 monograph Lymantria, became the basis for his theory of sex determination, which he developed from 1911 until 1931. Goldschmidt left Munich in 1914 for the position as head of the genetics section of the newly founded Kaiser Wilhelm Institute for Biology. During a field trip to Japan in 1914 he was not able to return to Germany due to the outbreak of the First World War and got stranded in the United States. He ended up in an internment camp in Fort Oglethorpe, Georgia for "dangerous Germans". After his release in 1918 he returned to Germany in 1919 and worked at the Kaiser Wilhelm Institute. Sensing that it was unsafe for him to remain in Germany he emigrated to the United States 1936, where he became professor at the University of California, Berkeley. During World War 2, the Nazi party published a propaganda poster entitled "Jewish World Domination" displaying the Goldschmidt family tree.

Goldschmidt was the first scientist to use the term "hopeful monster". He thought that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution. In his book The Material Basis of Evolution (1940), he wrote "the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation." Goldschmidt believed the large changes in evolution were caused by macromutations (large mutations). His ideas about macromutations became known as the hopeful monster hypothesis, which is considered a type of saltational evolution. According to Goldschmidt, biologists seem inclined to think that because they have not themselves seen a 'large' mutation, such a thing cannot be possible. But such a mutation need only be an event of the most extraordinary rarity to provide the world with the important material for evolution. The origin of the first eukaryotic cell might be considered an example of a Goldschmidtian hopeful monster.

See Also:

Dietrich, Michael R. 2003. Richard Goldschmidt: hopeful monsters and other 'heresies'. Nature reviews Genetics, 4:68-74.

Theodosius Dobzhansky (1900–1975)

Source: Wikipedia

Theodosius Grygorovych Dobzhanskywas a prominent Russian-American geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the unifying modern evolutionary synthesis. Dobzhansky was born in Ukraine, then part of the Russian Empire, and became an immigrant to the United States in 1927, aged 27 years old. His 1937 work Genetics and the Origin of Species became a major influence on the synthesis and was awarded the US National Medal of Science in 1964, and the Franklin Medal in 1973.

Dobzhansky immigrated to the United States in 1927 on a scholarship from the International Education Board of the Rockefeller Foundation to work and study in the United States. Arriving in New York City on December 27, he worked with Thomas Hunt Morgan at Columbia University, who had pioneered the use of fruit flies (Drosophila melanogaster) in genetics experiments. He followed Morgan to the California Institute of Technology from 1930 to 1940. On the basis of his experiments, he articulated the idea that reproductive isolation can be caused by differences in presence of microbial symbionts between populations. In 1937, he published one of the major works of the modern evolutionary synthesis, the synthesis of evolutionary biology with genetics, entitled Genetics and the Origin of Species, which amongst other things, defined evolution as "a change in the frequency of an allele within a gene pool". Dobzhansky's work was instrumental in spreading the idea that it is through mutations in genes that natural selection takes place. Also in 1937, he became a naturalized citizen of the United States. During this time, he had a very public falling out with one of his Drosophila collaborators, Alfred Sturtevant, based primarily in professional competition.

Dobzhansky's wife Natasha died of coronary thrombosis on February 22, 1969. Earlier (on June 1, 1968) Theodosius had been diagnosed with lymphocytic leukemia (a chronic form of leukemia), and had been given a few months to a few years to live. He retired in 1971, moving to the University of California, Davis where his student Francisco Jose Ayala had been made assistant professor, and where he continued working as an emeritus professor. He published one of his most famous essays "Nothing in Biology Makes Sense Except in the Light of Evolution" at this time, influenced by the paleontologist/priest Pierre Teilhard de Chardin. By 1975, his leukemia had become more severe, and on November 11 he traveled to San Jacinto, California for treatment and care. He died (of heart failure) on December 18.

See Also:

Theodosius Dobzhansky. 1973. Nothing in Biology Makes Sense except in the Light of Evolution. The American Biology Teacher, 35:125-129.

Collected papers from a NAS colloquium on Dobzhansky's Genetics and the Origin of Species

Francisco J. Ayala. 1985. Theodosius Dobzhansky 1900 – 1975. Biographical Memoirs, National Academy of Sciences.

Theodosius Dobzhansky Papers. Americal Philosophical Society

George Beadle (1903–1989)

Source: Wikipedia

George Wells Beadle was an American scientist in the field of genetics, and Nobel Prize in Physiology or Medicine Nobel laureate who with Edward Tatum discovered the role of genes in regulating biochemical events within cells in 1958. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. In 1931 Beadle was awarded a National Research Council Fellowship at the California Institute of Technology at Pasadena, where he remained from 1931 until 1936. During this period he continued his work on Indian corn and began, in collaboration with Professors Theodosius Dobzhansky, S. Emerson, and Alfred Sturtevant, work on crossing-over in the fruit fly, Drosophila melanogaster.

In 1935 Beadle visited Paris for six months to work with Professor Boris Ephrussi at the Institut de Biologie physico-chimique. Together they began the study of the development of eye pigment in Drosophila which later led to the work on the biochemistry of the genetics of the fungus Neurospora for which Beadle and Edward Lawrie Tatum were together awarded the 1958 Nobel Prize for Physiology or Medicine. In 1936 Beadle left the California Institute of Technology to become Assistant Professor of Genetics at Harvard University. A year later he was appointed Professor of Biology (Genetics) at Stanford University and there he remained for nine years, working for most of this period in collaboration with Tatum. In 1946 he returned to the California Institute of Technology as Professor of Biology and Chairman of the Division of Biology. Here he remained until January 1961 when he was elected Chancellor of the University of Chicago and, in the autumn of the same year, President of this University.

After retiring, Beadle undertook a remarkable experiment in maize genetics. In several laboratories he grew a series of Teosinte/Maize crosses. Then he crossed these progeny with each other. He looked for the rate of appearance of parent phenotypes among this second generation. The vast majority of these plants were intermediate between maize and Teosinte in their features, but about 1 in 500 of the plants were identical to either the parent maize or the parent teosinte. Using the mathematics of Mendelian genetics, he calculated that this showed a difference between maize and teosinte of about 5 or 6 genetic loci. This demonstration was so compelling that most scientists now agree that Teosinte is the wild progenitor of maize.

See Also:

Norman H. Horowitz. 1990. George Wells Beadle 1903 – 1989. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, "George W. Beadle's One Gene-One Enzyme Hypothesis". Embryo Project Encyclopedia (2014-05-23). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7892.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Ching Chun Li (1912–2003)

Source: Wikipedia

Ching Chun Li was a respected American population geneticist and human geneticist. Li was best known for his book An Introduction to Population Genetics and his teaching in human genetics. Ching Chun Li was born on October 27, 1912, in Taku, Tianjin, China. He received his BS degree in agronomy from the University of Nanking in 1936 and a PhD in plant breeding and genetics from Cornell University in 1940. He worked as post-doctorate fellows at Columbia University and North Carolina State University from 1940 to 1941. Li returned to China at the age of 30 and became the Professor of Genetics and Biometry at University of Nanking, his alma mater, in 1943. After World War II, he moved to Beijing for a Professorship of Agronomy at Peking University in 1946, where he finished An Introduction to Population Genetics in 1948. The book was the first notable publication where the population-genetics ideas of Ronald Fisher, Sewall Wright, and J. B. S. Haldane were brought together, synthesized, and presented in a coherent and readily understood manner.

See Also:

Aravinda Chakravarti. 2004. Ching Chun Li (1912–2003): A Personal Remembrance of a Hero of Genetics. The American Journal of Human Genetics, 74:789-792.

Eliot B. Spiess. 2005. Remembrance of Ching Chun Li, 1912–2003. Genetics, 169:9-11.

Matthias Jakob Schleiden (1804–1881)

Source: Wikipedia

Matthias Jakob Schleiden was a German botanist and co-founder of cell theory, along with Theodor Schwann and Rudolf Virchow. Born in Hamburg, Schleiden was educated at University of Jena, then practiced law in Heidelberg, but soon developed his love for botany into a full-time pursuit. Schleiden preferred to study plant structure under the microscope. While a professor of botany at the University of Jena, he wrote Contributions to our knowledge of phytogenesis (1838), in which he stated that all parts of the plant organism are composed of cells. Thus, Schleiden and Schwann became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, discovered in 1831 by the Scottish botanist Robert Brown, and sensed its connection with cell division. Schleiden was one of the first German biologists to accept Charles Darwin's theory of evolution. He became professor of botany at the University of Dorpat in 1863. He concluded that all plant parts are made of cells and that an embryonic plant organism arises from the one cell.

Theodor Schwann (1810–1882)

Source: Wikipedia

Theodor Schwann was a German physiologist. His many contributions to biology include the development of cell theory, the discovery of Schwann cells in the peripheral nervous system, the discovery and study of pepsin, the discovery of the organic nature of yeast, and the invention of the term metabolism. In 1837, Matthias Jakob Schleiden viewed and stated that new plant cells formed from the nuclei of old plant cells. While dining that year with Schwann, the conversation turned on the nuclei of plant and animal cells. Schwann remembered seeing similar structures in the cells of the notochord (as had been shown by Müller) and instantly realized the importance of connecting the two phenomena. The resemblance was confirmed without delay by both observers, and the results soon appeared in Schwann's famous Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants, in which he declared that "All living things are composed of cells and cell products". This became cell theory or cell doctrine. In the course of his verification of cell theory, Schwann proved the cellular origin and development of the most highly differentiated tissues including nails, feathers, and tooth enamel. Schwann established a basic principle of embryology by observing that the ovum is a single cell that eventually develops into a complete organism.

Rudolf Virchow (1821–1902)

Source: Wikipedia

Rudolf Ludwig Carl Virchow was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician, known for his advancement of public health. He is known as "the father of modern pathology" because his work helped to discredit humourism, bringing more science to medicine. He is also known as the founder of social medicine and veterinary pathology, and to his colleagues, the "Pope of medicine". A prolific writer, his scientific writings alone exceeded 2,000 in number. Among his books, Cellular Pathology published in 1858 is regarded as the root of modern pathology. This work also popularised the third dictum in cell theory: Omnis cellula e cellula ("All cells come from cells"); although his idea originated in 1855. Virchow is credited with several very important discoveries. His most widely known scientific contribution is his cell theory, which built on the work of Theodor Schwann. He was one of the first to accept the work of Robert Remak, who showed the origins of cells was the division of pre-existing cells. He did not initially accept the evidence for cell division, believing it only occurs in certain types of cells. When it dawned on him that Remak might be right, in 1855, he published Remak's work as his own, which caused a falling out between the two. This work, Virchow encapsulated in the epigram Omnis cellula e cellula ("all cells (come) from cells"), which he published in 1855. He was an ardent anti-evolutionist. He referred to Charles Darwin as an "ignoramus" and his own student Ernst Haeckel, the leading advocate of Darwinism in Germany, as a "fool". He discredited the original specimen of Neanderthal man as nothing but that of a deformed human, and not an ancestral species.

Walther Flemming (1843–1905)

Source: Wikipedia

Walther Flemming was a German biologist and a founder of cytogenetics. Flemming trained in medicine at University of Rostock, graduating in 1868. Afterwards, he served in 1870–71 as a military physician in the Franco-Prussian War. From 1873 to 1876 he worked as a teacher at the University of Prague. In 1876 he accepted a post as a professor of anatomy at the University of Kiel. He became the director of the Anatomical Institute and stayed there until his death. With the use of aniline dyes he was able to find a structure which strongly absorbed basophilic dyes, which he named chromatin. He identified that chromatin was correlated to threadlike structures in the cell nucleus – the chromosomes (meaning coloured bodies), which were named thus later by German anatomist Wilhelm von Waldeyer-Hartz (1841–1923). The Belgian scientist Edouard Van Beneden (1846–1910) had also independently observed chromosomes. Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread. However, he did not see the splitting into identical halves, the daughter chromatids. He studied mitosis both in vivo and in stained preparations, using as the source of biological material the fins and gills of salamanders. These results were published first in 1878 and in 1882 in the seminal book Zellsubstanz, Kern und Zelltheilung (Cell substance, nucleus and cell division). On the basis of his discoveries, Flemming surmised for the first time that all cell nuclei came from another predecessor nucleus (he coined the phrase omnis nucleus e nucleo, after Virchow's omnis cellula e cellula).

See Also:

Neidhard Paweletz. 2001. Walther Flemming: pioneer of mitosis research. Nature Reviews Molecular Cell Biology, 2:72-75. | doi:10.1038/35048077

Eduard Strasburger (1844–1912)

Source: Wikipedia

Eduard Adolf Strasburger was a Polish-German professor who was one of the most famous botanists of the 19th century. Strasburger studied biological sciences in Paris, Bonn and Jena, receiving a PhD in 1866 after working with Nathanael Pringsheim. In 1868 he taught at the University of Warsaw. In 1869 he was appointed professor of botany at the University of Jena. Since 1881 he was head of the Botanisches Institut at the University of Bonn. Together with Walther Flemming, and Edouard van Beneden he elucidated chromosome distribution during cell division.

Édouard van Beneden (1846–1910)

Source: Wikipedia

Édouard Joseph Louis Marie Van Beneden was a Belgian embryologist, cytologist and marine biologist. He was professor of zoology at the University of Liège. He contributed to cytogenetics by his works on the roundworm Ascaris. In this work he discovered and described the process of meiosis — a two-cell-division process by which cells reduce the number of chromosomes in preparation for the production of gametes. Van Beneden also elucidated, together with Walther Flemming and Eduard Strasburger, the essential facts of mitosis — the single-cell-division process that distributes equal chromosome complements to each of the two daughter cells.

Wilhelm von Waldeyer (1836–1921)

Source: Wikipedia

Heinrich Wilhelm Gottfried von Waldeyer-Hartz was a German anatomist, famous for consolidating the neuron theory of organization of the nervous system and for naming the chromosome. He is also remembered in two macroanatomical structures of the human body which were named after him: Waldeyer's tonsillar ring (the lymphoid tissue ring of the naso- and oropharynx) and Waldeyer's glands (of the eyelids). Waldeyer also studied the basophilic stained filaments which had been found (by his colleague of Kiel, Walther Flemming) to be the main constituents of chromatin, the material inside the cell nucleus. Although the full significance of chromosomes for genetics and for cell biology was still to be discovered, these filaments were known to be involved in the phenomenon of cell division discovered by Flemming, named mitosis, as well as in meiosis. In 1888, Waldeyer coined the term chromosome — colored body — to describe them.

See Also:

T. Cremer and C. Cremer. 1988. Centennial of Wilhelm Waldeyer’s introduction of the term “chromosome” in 1888. Cytogenetics and Cell Genetics, 48:66–67. (DOI:10.1159/000132591)

Waldeyer's 1888 paper in which he uses the word chromosome: Über Karyokinese und ihre Beziehungen zu den Befruchtungsvorgängen.

Oscar Hertwig (1849–1922)

Source: Wikipedia

Oscar Hertwig was a German zoologist and professor, who also wrote about the theory of evolution circa 1916, over 55 years after Charles Darwin's book The Origin of Species. Oscar Hertwig was a leader in the field of comparative and causal animal-developmental history. He also wrote a leading textbook. By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell. He recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he published his findings that fertilization includes the penetration of a spermatozoon into an egg cell. Oscar Hertwig experiments with frog eggs revealed the 'long axis rule', or Hertwig rule. According to this rule cell divides along its long axis (1884). While Oscar was well interested in developmental biology, he was opposed to chance as assumed in Charles Darwin´s theory. His most important theoretical book was: Das Werden der Organismen, eine Widerlegung der Darwinschen Zufallslehre (Jena, 1916) (translation: The Origin of Organisms – a Refutation of Darwin's Theory of Chance).

See Also:

Brind'Amour, Katherine,, Garcia, Benjamin, "Wilhelm August Oscar Hertwig (1849-1922)". Embryo Project Encyclopedia (2007-11-01). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1707.

Churchill, F B (1970), "Hertwig, Weismann, and the meaning of reduction division circa 1890.", Isis; an international review devoted to the history of science and its cultural influences, 61:429–57.

August Weismann (1834–1914)

Source: Wikipedia

August Friedrich Leopold Weismann was a German evolutionary biologist. Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg. His main contribution involved his Germ Plasm Theory, at one time also known as Weismannism, according to which inheritance (in a multicellular organism) only takes place by means of the germ cells — the gametes such as egg cells and sperm cells. Other cells of the body — somatic cells — do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. The idea of the Weismann barrier is central to the modern evolutionary synthesis, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection. Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time".

See Also:

Essays Upon Heredity — a collection of Weismann's writing on hereditary issues.

Yawen Zou. 2015. The Germ-Plasm: a Theory of Heredity (1893), by August Weismann. The Embryo Project Encyclopedia.

Edwin G. Conklin. 1915. August Weismann. Proceedings of the American Philosophical Society, 54:3-12.

Edmund Beecher Wilson (1856–1939)

Source: Wikipedia

Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell in Development and Inheritance. He and Nettie Maria Stevens were the first researchers to describe the chromosomal basis of sex, but they conducted their research independently of each other. Wilson is credited as America's first cell biologist. In 1898 he used the similarity in embryos to describe phylogenetic relationships. By observing spiral cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells and concluded that all these organisms must have a common ancestor.

Theodor Boveri (1862–1915)

Source: Embryo Project

Theodor Heinrich Boveri was a German biologist. He was notable for first hypothesising the cellular processes that cause cancer. Boveri's work with sea urchins showed that it was necessary to have all chromosomes present in order for proper embryonic development to take place. This discovery was an important part of the Boveri–Sutton chromosome theory, which identifies chromosomes as the carriers of genetic material. The theory correctly explains the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors (particles) required by Mendel's laws. The chromosome theory of inheritance is credited to papers by Walter Sutton in 1902 and 1903, as well as to independent work by Theodor Boveri during roughly the same period. Boveri's thoughts are summarized in his book Ergebnisse über die Konstitution der chromatischen Substanz des Zellkerns (Results on the constitution of the chromatic substance of the cell nucleus), Jena: Verlag von Gustav Fischer, 1904. His other significant discovery was the centrosome (1888), which he described as the especial organ of cell division. Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode Parascaris.

Clarence Erwin McClung (1870–1946)

Source: Wikipedia

Clarence Erwin (CE) McClung was an American zoologist of wide-ranging interests. Although born in California, he spent much of his early life in Kansas. He originally studied pharmacy at Kansas University, receiving the Ph.G. degree in 1892. He taught pharmacy at the University for a year, but then his interest shifted to more general biological questions and he reenrolled as a student. From Kansas University he received the A.B. degree in 1896, the A.M. in 1898, and the Ph.D. in 1902. CE McClung made important contributions to early genetics, but he was also a general zoologist and paleontologist who received all of his degrees from Kansas and then spent his early career on the faculty there, ultimately assuming the positions of chair of the zoology department, curator of vertebrate paleontology, and even acting dean of the medical school. Early in his career, he undertook an investigation of spermatogenesis in Ziphidium fasciatum, a long-horned grasshopper. In this material he recognized that an object thought by some to be a nucleolus was actually an unpaired chromosome. Although others had noticed that this object was distributed asymmetrically into some but not all spermatozoa, McClung was the first to see that this could provide a cytological mechanism of sex determination.

See Also:

D. H. Wenrich. 1946. Clarence Erwin McClung 1870-1946 Science, 103:551-552. DOI: 10.1126/science.103.2679.551

David Henry Wenrich Papers: A collection largely developed to support the Dr. Wenrich's efforts to honor Dr. Clarence Erwin McClung.

Walter S. Sutton (1877–1916)

Source: The Electronic Scholarly Publishing Project

Walter Stanborough Sutton was an American geneticist and physician whose most significant contribution to present-day biology was his theory that the Mendelian laws of inheritance could be applied to chromosomes at the cellular level of living organisms. This is now known as the Boveri-Sutton chromosome theory.

After graduating high school in Russell, he enrolled at the University of Kansas in engineering in 1896. Following the death of his younger brother (John) from typhus in 1897, Sutton switched his major to biology with an interest in medicine. While at the University of Kansas, both he and his older brother, William Sutton, played basketball for Dr. James Naismith. Sutton distinguished himself as student being elected to both Phi Beta Kappa and Sigma Xi and receiving both bachelor's and master's degrees by 1901. For his Masters thesis, he studied the spermatogenesis of Brachystola magna, a large grasshopper indigenous to the farmlands upon which Sutton was raised.

Considering the advice of his mentor at KU, Dr. C. E. McClung, Sutton moved to Columbia University for further study of zoology under Dr. Edmund B. Wilson. It was here that Sutton wrote his two significant works in genetics – “On the morphology of the chromosome group in Brachystola magna” and “The chromosomes in heredity”. The German biologist Theodor Boveri independently reached the same conclusions as Sutton, and their concepts are often referred to as the Boveri-Sutton chromosome theory. Sutton’s hypothesis was widely accepted by most scientists, particularly cytologists, at the time. The continued work of Thomas Hunt Morgan at Columbia brought the theory to universal acceptance by 1915 through his studies of Drosophila melanogaster, the fruit fly, even as William Bateson continued to question the theory until 1921. Sutton did not complete his PhD in Zoology as he originally planned. At the age of 26, he returned to the Kansas oil fields for 2 years. There he was able to perfect a device to start large gas engines with high pressure-gas and develop hoisting apparatuses for deep wells. Sutton’s mechanical aptitudes never left him. His father finally directed him to return to his medical studies and he did so returning to Columbia University in 1905. Sutton’s medical studies proceeded through the College of Physicians and Surgeons at Columbia University. While he continued to work on patents associated with oil drilling, Sutton also began at this stage to apply his mechanical aptitude to improving medical instruments. With credit for his graduate studies at both the University of Kansas and Columbia University, Sutton obtained his doctorate in medicine in 1907 graduating with “high standing”. He then began an internship at Roosevelt Hospital in New York working in the surgical division headed by Dr. Joseph Blake.

In 1909, Sutton returned to Kansas City, Kansas where his family had relocated and his father and brother were in law practice. Sutton was appointed assistant professor of surgery at the four-year-old University of Kansas Medical School. The tenuous nature of the appointment at the young school led him to also maintain a private practice and serve on the staff of St. Margaret’s Hospital as well as the University’s Bell Memorial Hospital. For six years, Sutton performed a wide range of surgeries carefully documenting the procedures. He published several articles related to these cases going back to his internship at Roosevelt. In 1911, he had accepted a commission as a First Lieutenant in the United States Army Medical reserve Corps. This eventually led to his taking a leave of absence from the University in February, 1915 to serve at the American Ambulance Hospital outside Paris. Sutton and others from his days at Columbia and Roosevelt arrived at College of Juilly on February 23 where hospital facilities had been set up only 40 miles from the front lines of World War I. Within 2 months, he was surgeon-in-chief handling administrative duties in addition to his surgical responsibilities. His inventive aptitude was perhaps never more valued as he developed fluoroscopic techniques to identify and localize shrapnel within the soldier’s bodies and then removed the foreign items with instruments of his own design. After his return, he documented these techniques in Binnie’s Manual of Operative Surgery.[11] Sutton’s return sailing from France was on June 26, 1915 having stayed only four months, but have made a significant contribution to wartime medical treatment. Dr. Sutton died rather unexpectedly at the age of 39 due to complications from acute appendicitis.

See Also:

Sutton, Walter S. 1902. On the morphology of the chromosome group in Brachystola magna. Biological Bulletin, 4:24-39.

Sutton, Walter S. 1903. The chromosomes in heredity. Biological Bulletin, 4: 231-251.

WIKIPEDIA: Walter Sutton

Crow, JF and Crow, EW 2002. 100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity. Genetics, 160:1-4.

The Embryo Project Encyclopedia: Walter Stansborough Sutton (1877–1916)

Hulston, Nancy Walter S. Sutton, MD: A Genius Goes To War

McKusick, Victor A. 1960. Walter S. Sutton and the Physical Basis of Mendelism. Bulletin of the History of Medicine, 34: 487.

Nettie Marie Stevens (1861–1912)

Source: Wikipedia

Nettie Maria Stevens was an early American geneticist. In 1906, she discovered that male beetles produce two kinds of sperm, one with a large chromosome and one with a small chromosome. When the sperm with the large chromosome fertilized eggs, they produced female offspring, and when the sperm with the small chromosome fertilized eggs, they produced male offspring. This pattern was observed in other animals, including humans, and became known as the XY sex-determination system.

See Also:

Smith, Kaitlin, "Nettie Maria Stevens (1861-1912)". Embryo Project Encyclopedia (2010-06-20). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/2028.

Thomas H. Montgomery, Jr. (1873–1912)

Source: Wikipedia

Thomas Harrison Montgomery Jr. was an American zoologist who made important contributions to cell biology–especially in chromosomes and their roles in sex determination–as well as the biology of birds and several groups invertebrates, naming many species of ribbon worms, rotifers, and spiders. He studied in Berlin before becoming a researcher and professor at the University of Pennsylvania, where he primarily worked until his death at the age of 39. In his short career he published 80 scientific papers and two books.

Harrison published 25 papers on cell biology, primarily using insect cells. His most notable research includes early observations of the pairing of maternal and paternal chromosomes during cell division. He was first to propose that chromosomes play the dominant role in sex determination, although he rejected the idea that sex was determined by chromosomes alone, and some historians claim he was the first to propose the chromosome theory of inheritance, an idea widely credited to Walter Sutton and Theodor Boveri. He also detailed the morphology of the nucleolus, and observed that in some hemipteran insects the germ cells of males but not females contain odd numbers of chromosomes, which is now known to influence sex-determination, A resolution of the American Society of Zoologists read after his death stated "it would be impossible to write a text-book upon the role of the chromosomes in the determination of sex without referring to his crucial labors in this field."

See Also:

Conklin, Edwin G. 1913. PROFESSOR THOMAS HARRISON MONTGOMERY, JR. Science, 38:207-214. DOI: 10.1126/science.38.972.207

Montgomery, Thos. H., Jr. 1910. ARE PARTICULAR CHROMOSOMES SEX DETERMINANTS? Biological Bulletin, 19:1-17.

Theophilus S. Painter (1889–1969)

Source: Wikipedia

Theophilus Shickel Painter was an American zoologist best-known for his work on the structure and function of chromosomes, especially the sex-determination genes X and Y in humans. He also carried out work in identifying genes in fruit flies (Drosophila). His work exploited the giant polytene chromosomes in the salivary glands of Drosophila and other Dipteran larvae. Painter joined the faculty at the University of Texas in 1916 and, except for military duty during World War I, stayed there his whole career. He was, in succession, associate professor, professor and distinguished professor of zoology. He served as acting president (1944–1946) and president (1946–1952) of the University of Texas and retired from active teaching in 1966.

Harriet Creighton (1909–2004)

Courtesy of Cold Spring Harbor Laboratory Archives. Noncommercial, educational use only.

Source: Wikipedia

Harriet Baldwin Creighton was an American botanist, geneticist and educator. Born in Delavan, Illinois, Creighton graduated from Wellesley College in 1929, and went on to complete her Ph.D. at Cornell University in 1933. During her time at Cornell she worked in the field of maize cytogenetics with Barbara McClintock, the pair published a very influential paper in 1931 in which they described chromosomal crossover for the first time. This paper, part of her Ph.D. research, provided key evidence that chromosomes carried and exchanged genetic information and hence that genes for physical traits are carried on chromosomes. Barbara McClintock guided her Ph.D. research. After completing her Ph.D. she taught at Cornell University and Connecticut College, and then returned to Wellesley where she taught until her retirement in 1974; taking time from her career to serve in the U.S. Navy during World War II.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Kass, Lee B. 2005c. Harriet B. Creighton: Proud botanist. Plant Science Bulletin. 51: 118-125. Available online, December 2005:

Barbara McClintock (1902–1992)

Source: Wikipedia

Barbara McClintock was an American scientist and cytogeneticist who was awarded the 1983 Nobel Prize in Physiology or Medicine. McClintock received her PhD in botany from Cornell University in 1927. There she started her career as the leader in the development of maize cytogenetics, the focus of her research for the rest of her life. From the late 1920s, McClintock studied chromosomes and how they change during reproduction in maize. She developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas. One of those ideas was the notion of genetic recombination by crossing-over during meiosis — a mechanism by which chromosomes exchange information. In 1930, McClintock was the first person to describe the cross-shaped interaction of homologous chromosomes during meiosis. The following year, McClintock and Creighton proved the link between chromosomal crossover during meiosis and the recombination of genetic traits. They observed how the recombination of chromosomes seen under a microscope correlated with new traits. Until this point, it had only been hypothesized that genetic recombination could occur during meiosis, although it had not been shown genetically. McClintock received a fellowship from the Guggenheim Foundation that made possible six months of training in Germany during 1933 and 1934. She had planned to work with Curt Stern, who had demonstrated crossing-over in Drosophila just weeks after McClintock and Creighton had done so; however, Stern emigrated to the United States. Instead, she worked with geneticist Richard B. Goldschmidt, who was the head of the Kaiser Wilhelm Institute. She left Germany early amidst mounting political tension in Europe, and returned to Cornell, remaining there until 1936, when she accepted an Assistant Professorship offered to her by Lewis Stadler in the Department of Botany at the University of Missouri-Columbia. She produced the first genetic map for maize, linking regions of the chromosome to physical traits. She demonstrated the role of the telomere and centromere, regions of the chromosome that are important in the conservation of genetic information. She was recognized among the best in the field, awarded prestigious fellowships, and elected a member of the National Academy of Sciences in 1944.

See Also:

McClintock, Barbara. 1931. The order of the genes C, Sh, and Wx in Zea mays with reference to a cytologically known point in the chromosome. PNAS, 17:485-491.

Creighton, Harriet B., and McClintock, Barbara. 1931. A correlation of cytological and genetical crossing-over in Zea mays. PNAS, 17:492-497.

Creighton, Harriet B., and McClintock, Barbara. 1935. A correlation of cytological and genetical crossing-over in Zea mays. A corroboration. PNAS, 21:148-150.

Edward Coe and Lee B. Kass (2005) Proof of physical exchange of genes on the chromosomes. Proceedings of the National Academy of Sciences, USA. 102:6641-6646.

Edward Coe. 2001. The origins of maize genetics. Nature Reviews Genetics, 2:898-905 | doi:10.1038/35098524

Barbara McClintock, DNA Learning Center

Archibald Garrod (1857–1938)

Source: Wikipedia

Sir Archibald Edward Garrod was an English physician who pioneered the field of inborn errors of metabolism. He also discovered alkaptonuria, understanding its inheritance. He served as Regius Professor of Medicine at the University of Oxford from 1920 to 1927. Garrod is best known for his scientific study of inborn errors of metabolism. He developed an increasing interest in chemical pathology, and investigated urine chemistry as a reflection of systemic metabolism and disease. This research, combined with the new understanding of Mendelian inheritance, evolved from an investigation of a few families with an obscure and not very dangerous disease (alkaptonuria) to the realization that a whole territory of mysterious diseases might be understood as inherited disorders of metabolism. Working with William Bateson, Garrod came to understand the pattern of alkaptonuria appearance in children based on Mendelian principles. Once he applied Mendel’s concepts to alkaptonuria, he published a paper in 1902 called The Incidence of Alkaptonuria: A Study of Chemical Individuality. In the paper, Garrod explains how he came to understand the condition and speculates as to its causes. He cites various case studies and compares alkaptonuria to albinism in how it is inherited. He summarized his thoughts on the relationship of inheritance to metabolic disease in his book Inborn Errors of Metabolism .

See Also:

F. G. Hopkins. 1938. Archibald Edward Garrod. 1857–1936. Biographical Memoirs of fellows of the Royal Society, 2:225–228.

Krishna Dronamraju. 1992. BIOGRAPHY Profiles in Genetics: Archibald E. Garrod (1857-1936). american Journal of Human Genetics, 51:216-219.

Boris Ephrussi (1901–1979)

Source: Wikipedia

Boris Ephrussi, Professor of Genetics at the University of Paris, was a Russo-French geneticist. Boris started his scientific training as a Russian émigré in 1920. He studied the initiation and regulation of embryological processes by intracellular and extracellular factors. A major strand of his early research concerned the effect of temperature on the development of fertilized sea urchin eggs. During Ephrussi's time, writing a second dissertation was standard practice in France. Ephrussi's involved culturing tissues. Ephrussi ran into difficulties typically associated with early tissue culture techniques, but despite these obstacles Ephrussi managed to conclude from studies of brachyury in mice that intrinsic factors (i.e. genes) play a key role in development.

As the next phase of his career, Ephrussi coupled his embryological concerns with a firm conviction that one must understand the role of genes in order to decipher embryological processes. He moved to Caltech in 1934 and stayed until 1935 to learn genetics within the intellectual empire of T.H. Morgan. This move was supported by the Rockefeller Foundation. During this period he conducted important work with George Beadle, who joined him in Paris in the autumn of 1935. There they produced results from experiments with Drosophila eye transplants. This became integral to the work of Beadle and Tatum, who were working with Neurospora, and from this research developed the one gene, one enzyme hypothesis.

See Also:

Chhetri, Divyash, "Beadle and Ephrussi's Transplantation Technique for Drosophila". Embryo Project Encyclopedia (2014-06-29). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/8015.

George Beadle (1903–1989)

Source: Wikipedia

George Wells Beadle was an American scientist in the field of genetics, and Nobel Prize in Physiology or Medicine Nobel laureate who with Edward Tatum discovered the role of genes in regulating biochemical events within cells in 1958. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. In 1931 Beadle was awarded a National Research Council Fellowship at the California Institute of Technology at Pasadena, where he remained from 1931 until 1936. During this period he continued his work on Indian corn and began, in collaboration with Professors Theodosius Dobzhansky, S. Emerson, and Alfred Sturtevant, work on crossing-over in the fruit fly, Drosophila melanogaster.

In 1935 Beadle visited Paris for six months to work with Professor Boris Ephrussi at the Institut de Biologie physico-chimique. Together they began the study of the development of eye pigment in Drosophila which later led to the work on the biochemistry of the genetics of the fungus Neurospora for which Beadle and Edward Lawrie Tatum were together awarded the 1958 Nobel Prize for Physiology or Medicine. In 1936 Beadle left the California Institute of Technology to become Assistant Professor of Genetics at Harvard University. A year later he was appointed Professor of Biology (Genetics) at Stanford University and there he remained for nine years, working for most of this period in collaboration with Tatum. In 1946 he returned to the California Institute of Technology as Professor of Biology and Chairman of the Division of Biology. Here he remained until January 1961 when he was elected Chancellor of the University of Chicago and, in the autumn of the same year, President of this University.

After retiring, Beadle undertook a remarkable experiment in maize genetics. In several laboratories he grew a series of Teosinte/Maize crosses. Then he crossed these progeny with each other. He looked for the rate of appearance of parent phenotypes among this second generation. The vast majority of these plants were intermediate between maize and Teosinte in their features, but about 1 in 500 of the plants were identical to either the parent maize or the parent teosinte. Using the mathematics of Mendelian genetics, he calculated that this showed a difference between maize and teosinte of about 5 or 6 genetic loci. This demonstration was so compelling that most scientists now agree that Teosinte is the wild progenitor of maize.

See Also:

Norman H. Horowitz. 1990. George Wells Beadle 1903 – 1989. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, "George W. Beadle's One Gene-One Enzyme Hypothesis". Embryo Project Encyclopedia (2014-05-23). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7892.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Edward Tatum (1909–1975)

Source: Wikipedia

Edward Lawrie Tatum was an American geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Beadle for showing that genes control individual steps in metabolism. The other half of that year's award went to Joshua Lederberg. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments, published in 1941, led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. This became a fundamental concept in physiological genetics. Tatum went on to study genetics in bacteria. An active area of research in his laboratory was to understand the basis of Tryptophan biosynthesis in Escherichia coli. Later, Tatum and his student Joshua Lederberg showed that E. coli could share genetic information through recombination. This became a fundamental concept in microbial genetics.

See Also:

Joshua Lederberg. 1990. Edward Lawrie Tatum 1909 – 1975. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Frederick Twort (1877–1950)

Source: Wikipedia

Frederick William Twort was an English bacteriologist and was the original discoverer in 1915 of bacteriophages (viruses that infect bacteria). He studied medicine at St Thomas's Hospital, London, was superintendent of the Brown Institute for Animals (a pathology research centre), and was a professor of bacteriology at the University of London. He researched into Johne's disease, a chronic intestinal infection of cattle, and also discovered that vitamin K is needed by growing leprosy bacteria.

Early in the history of microbiology, bacteria were often differentiated testing their ability to grow on different media. Twort's first important paper found some shortcomings to this method. He found that the major subgroups identified by sugar fermentation were not capable of clear-cut subdivision by tests on glucosides, nor even were they strictly separable by sugars. Twort wrote, "It seems, therefore, probable that the separate micro-organisms in the various subgroups are not to be regarded as distinct species, but as varieties or hybrids of one or more species. If this be so, one might expect them to be constantly varying, losing old characters and gaining new ones according to the conditions under which they are grown, and it was with the object of testing this hypothesis that further series of experiments were undertaken." Following prolonged incubation in media that they previously failed to ferment, several species acquired fermentation powers which originally they did not enjoy. We now know that these mutant individuals able to ferment novel sugars arose in culture, and came to dominate the population. Although ignored at the time — a trend that seemed to plague his career — this work was quite prescient, and anticipated by decades the subsequent work on adaptation and mutation by bacterial chemists and microbiologists.

Twort and his brother, Dr. C. C. Twort, had for some years been trying to grow viruses in artificial media hoping to find a nonpathogenic virus, which might be the wild type of a pathogenic one, so more likely to grow. In 1914, Twort set out to identify the elusive (now known to be nonexistent) "essential substance" that would allow vaccinia virus to grow in vitro. At the time, smallpox vaccines had to be made in the skin of calves and was almost always contaminated with the bacterial genus Staphylococcus. Twort speculated the contaminating bacteria might be the source of the "essential substance" needed by vaccinia to survive. He plated some of the smallpox vaccines on nutrient agar slants and obtained large bacterial colonies of several colours. Upon closer examination of the colonies with a magnifying glass, he found minute glassy areas that would not grow when subcultured. He quickly realized these glassy areas were the result of the destruction of the bacterial cells and was able to pick from some of these areas and transmit this from one staphylococci colony to another.

Further experiments showed the agent could pass through porcelain filters and it required bacteria for growth. These observations show Twort had discovered most of the essential features of bacteriophages, although Twort seemed to favor the idea that the principle was not a separate form of life, but an enzyme which is secreted by the bacteria. Twort published these results in The Lancet in 1915 and called the contagion the bacteriolytic agent. Unfortunately, his discovery was ignored; Félix d'Herelle discovered phages independently, and Twort's work may have been lost to time, but for Jules Bordet and Andre Gratia's rediscovery of Twort's paper.

See Also:

Duckworth, D. H. 1976. "Who discovered bacteriophage?". Bacteriological Reviews. 40:793–802.

Félix d'Herelle (1873–1949)

Source: Wikipedia

Félix d'Herelle was a French-Canadian microbiologist. He was co-discoverer of bacteriophages (viruses that infect bacteria) and experimented with the possibility of phage therapy. D'Herelle has also been credited for his contributions to the larger concept of applied microbiology.

In 1915, British bacteriologist Frederick W. Twort discovered a small agent that infects and kills bacteria, but did not pursue the issue further. Independently, the discovery of "an invisible, antagonistic microbe of the dysentery bacillus" by d'Herelle was announced on September 3, 1917. The isolation of phages by d'Herelle works like this: (1) Nutritional medium is infected with bacteria; the medium turns opaque; (2) The bacteria are infected with phages and die, producing new phages; the medium clears up; and (3) The medium is filtered through porcelain filter, holding back bacteria and larger objects; only the smaller phages pass through.

In early 1919, d'Herelle isolated phages from chicken feces, successfully treating a plague of chicken typhus with them. After this successful experiment on chicken, he felt ready for the first trial on humans. The first patient was healed of dysentery using phage therapy in August 1919. Many more followed. At the time, no one, not even d'Herelle, knew exactly what a phage was. D'Herelle claimed that it was a biological organism that reproduces, somehow feeding off bacteria. Others, the Nobelist Jules Bordet chief among them, theorized that phages were inanimate chemicals, enzymes specifically, that were already present in bacteria, and only trigger the release of similar proteins, killing the bacteria in the process. Due to this uncertainty, and d'Herelle using phages without much hesitation on humans, his work was under constant attack from many other scientists. It was not until the first phage was observed under an electron microscope by Helmut Ruska in 1939 that its true nature was established.

D'Herelle became widely known for his imaginative approaches to important problems in theoretical, as well as applied, microbiology. At the same time, he was widely reviled for his self-advertisement, his exaggerated claims of success and his sharp financial practices. He also had a talent for making enemies among powerful senior scientists. D'Herelle's main legacy lies in the use of phage in the molecular revolution in biology.

See Also:

Duckworth, D. H. 1976. "Who discovered bacteriophage?". Bacteriological Reviews. 40:793–802.

Frederick Griffith (1879–1941)

Source: Wikipedia

Frederick Griffith was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function. He showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. The observation was attributed to an unidentified transforming principle or transforming factor. This was later identified as DNA. America's leading pneumococcal researcher, Oswald T. Avery, speculated that Griffith had failed to apply adequate controls. A cautious and thorough researcher, and a reticent individual, Griffith's tendency was to publish only findings that he believed truly significant, and Griffith's findings were rapidly confirmed by researchers in Avery's laboratory. His discovery was one of the first to show the central role of DNA in heredity.

Griffith's experiment showed that one strain, R (rough, non-virulent) of bacteria could be transformed to exhibit the attributes of a different strain S (smooth, virulent),through exposure to material from dead members of the other strain. Specifically, he found that if he injected live R bacteria into mice, the mice lived (no surprise, R bacteria are non-virulent). He also found that if he injected deda S bacteria into mice, the mice lived (again, no surprise, dead bacteria do not cause disease). However, if he injected mice with a combination of live R and dead S, the mice died from an infection of live S bacteria. It appeared that exposure to dead S bacteria had transformed live R into live S bacteria.

This stunning result seemed to prove that there was some non-living, physical basis to bacteria hereditary — some molecular carrier of genetic information — that was being lost from the dead S bacteria and picked up by the live R bacteria, allowing the R to transform into S. Now the question became, What is the nature of that hereditary molecule?

In 1944, work by Oswald Avery, Colin MacLeod, and Maclyn McCarty, showed that DNA is the substance that causes bacterial transformation.

See Also:

Griffith's Experiment, Explained

The Avery–MacLeod–McCarty experiment

Milislav Demerec (1895–1966)

Source: Wikipedia

Milislav Demerec (January 11, 1895 – April 12, 1966) was a Croatian-American geneticist, and the director of the Department of Genetics, Carnegie Institution of Washington [CIW], now Cold Spring Harbor Laboratory (CSHL) from 1941 to 1960, recruiting Barbara McClintock and Alfred Hershey. Demerec was born and raised in Kostajnica (then Austria-Hungary, now Croatia). He attended College of Agriculture in Križevci, graduating in 1916. He worked at Križevci Experiment Station, and then attended the College of Agriculture in Grignon, France after World War I. He emigrated to the United States for graduate studies in 1919. In 1919 he started his PhD at Cornell University, his work was on maize genetics and was supervised by Rollins A. Emerson. He completed his PhD in 1923 and took up a research position at the Carnegie Institution of Washington's [CIW] Department of Genetics, now Cold Spring Harbor Laboratory. He completed work from his PhD, showing that ten different alleles could cause albinism in maize kernels, the at the advice of C. W. Metz he began work on the genetics of the plant Delphinium and the fruit fly Drosophila virilis studying mosaicism.

He became a prominent Drosophila researcher and established the Drosophila Information Service newsletter in 1934 with Calvin Bridges. In 1936 he was made the assistant directory of the Department of Genetics, and the acting director in 1941 following the retirement of Albert Blakeslee. That year, he was also made director of the Biological Laboratory of the Long Island Biological Association making him the director of both Cold Spring Harbor laboratories, by 1943.

After overcoming opposition from Thomas Hunt Morgan, Demerec oversaw the completion of much of the late Calvin Bridges’s work. Demerec appointed Katherine Brehme Warren to complete The Mutants of Drosophila melanogaster (1944) and the book became a classic in the field.

In the 1940s the direction of Demerec's research changed to the genetics of bacteria and their viruses after a symposium given by Max Delbrück. During World War II he used his knowledge of bacterial genetics to increase the yield from the Penicillium. Following the war he continued to work on bacterial genetics and the problem of antibiotic resistance in E. coli, Salmonella, and Staphylococcus. In 1946 he was elected to the National Academy of Sciences, and in 1947 became the founding editor of Advances in Genetics, the first journal to review the finding of modern genetics. In the 1950s he served on the genetics panel of the National Academy of Sciences' Committee on the Biological Effects of Atomic Radiation. In 1952 he was elected to the American Philosophical Society.

See Also:

Demerec, Milislav. 1933. What is a Gene? Journal of Heredity, 24:368-378.

Cyril Hinshelwood (1897–1967)

Source: Wikipedia

Sir Cyril Norman Hinshelwood was an English physical chemist and a Nobel Prize laureate. During the First World War, Hinshelwood was a chemist in an explosives factory. He was a tutor at Trinity College, Oxford from 1921 to 1937 and was Dr Lee's Professor of Chemistry at the University of Oxford from 1937. He served on several Advisory Councils on scientific matters to the British Government. His early studies of molecular kinetics led to the publication of Thermodynamics for Students of Chemistry and The Kinetics of Chemical Change in 1926. With Harold Warris Thompson he studied the explosive reaction of hydrogen and oxygen and described the phenomenon of chain reaction. His subsequent work on chemical changes in the bacterial cell proved to be of great importance in later research work on antibiotics and therapeutic agents, and his book, The Chemical Kinetics of the Bacterial Cell was published in 1946, followed by Growth, Function and Regulation in Bacterial Cells in 1966. In 1951 he published The Structure of Physical Chemistry. It was republished as an Oxford Classic Texts in the Physical Sciences by Oxford University Press in 2005.

Hinshelwood applied physical-chemistry thinking to bacteria and became convinced that bacteria possessed no true genetic apparatus and therefore exhibited no formal patterns of inheritance. He argued that apparent adaptive changes in bacterial populations (e.g., the emergence of antibiotic resistance) could be explained by a process involving shifts in stable chemical equilibria, induced by exposure to diufferent environmental conditions. He referred to this process as training.

This mistaken belief dominated thought about microbial genetics until Joshua Lederberg and Edward Tatum showed that genetic recombination can be detected among bacteria.

See Also:

The Nobel Prize in Chemistry 1956 was awarded jointly to Sir Cyril Norman Hinshelwood and Nikolay Nikolaevich Semenov for their researches into the mechanism of chemical reactions.

Salvador Luria (1912–1991)

Source: Wikipedia

Salvador Edward Luria was an Italian microbiologist, later a naturalized U.S. citizen. He won the Nobel Prize in Physiology or Medicine in 1969, with Max Delbrück and Alfred Hershey, for their discoveries on the replication mechanism and the genetic structure of viruses. Salvador Luria also showed that bacterial resistance to viruses (phages) is genetically inherited. Luria was born Salvatore Edoardo Luria, in Turin, Italy to an influential Italian Sephardi Jewish family. His parents were Ester (Sacerdote) and Davide Luria. He attended the medical school at the University of Turin studying with Giuseppe Levi. There, he met two other future Nobel laureates: Rita Levi-Montalcini and Renato Dulbecco. He graduated from the University of Turin in 1935. From 1936 to 1937, Luria served his required time in the Italian army as a medical officer. He then took classes in radiology at the University of Rome. Here, he was introduced to Max Delbrück's theories on the gene as a molecule and began to formulate methods for testing genetic theory with the bacteriophages, viruses that infect bacteria. In 1938, he received a fellowship to study in the United States, where he intended to work with Delbrück. Soon after Luria received the award, Benito Mussolini's fascist regime banned Jews from academic research fellowships. Without funding sources for work in the U.S. or Italy, Luria left his home country for Paris, France in 1938. As the Nazi German armies invaded France in 1940, Luria fled on bicycle to Marseille where he received an immigration visa to the United States.

Luria arrived in New York City on September 12, 1940, and soon changed his first and middle names. With the help of physicist Enrico Fermi, whom he knew from his time at the University of Rome, Luria received a Rockefeller Foundation fellowship at Columbia University. He soon met Delbrück and Hershey, and they collaborated on experiments at Cold Spring Harbor Laboratory and in Delbrück's lab at Vanderbilt University. His famous experiment with Delbrück in 1943, known as the Luria–Delbrück experiment, demonstrated statistically that inheritance in bacteria must follow Darwinian rather than Lamarckian principles and that mutant bacteria occurring randomly can still bestow viral resistance without the virus being present. The idea that natural selection affects bacteria has profound consequences, for example, it explains how bacteria develop antibiotic resistance. From 1943 to 1950, he worked at Indiana University. His first graduate student was James D. Watson, who went on to discover the structure of DNA with Francis Crick. In January 1947, Luria became a naturalized citizen of the United States.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Julian Huxley (1887–1975)

Source: Wikipedia

Sir Julian Sorell Huxley was a British evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern evolutionary synthesis. He was secretary of the Zoological Society of London (1935–1942), the first Director of UNESCO, a founding member of the World Wildlife Fund and the first President of the British Humanist Association. Huxley came from the distinguished Huxley family. His brother was the writer Aldous Huxley, and his half-brother a fellow biologist and Nobel laureate, Andrew Huxley; his father was writer and editor Leonard Huxley; and his paternal grandfather was Thomas Henry Huxley, a friend and supporter of Charles Darwin and proponent of evolution. His maternal grandfather was the academic Tom Arnold, his great-uncle was poet Matthew Arnold and his great-grandfather was Thomas Arnold of Rugby School.

Huxley was one of the main architects of the modern evolutionary synthesis which took place around the time of World War II. The synthesis of genetic and population ideas produced a consensus which reigned in biology from about 1940, and which is still broadly tenable. His book Evolution: The Modern Synthesis was written while he was secretary to the Zoological Society, and made use of his remarkable collection of reprints covering the first part of the century. It was published in 1942. Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing". Huxley's main co-respondents in the modern evolutionary synthesis are usually listed as Ernst Mayr, Theodosius Dobzhansky, George Gaylord Simpson, Bernhard Rensch, Ledyard Stebbins and the population geneticists J. B. S. Haldane, Ronald Fisher and Sewall Wright.

Despite its ecstatic initial reception, the limits of Huxley's Modern Synthesis are now becoming more obvious. A particular problem is the book's completely inadequate treatment of microbial genetics:

Bacteria ... appear to be not only wholly asexual but premitotic. Their hereditary constitution is not differentiated into specialized parts with different functions. They have no genes in the sense of accurately quantized portions of hereditary substance; and therefore they have no need for the accurate division of the genetic system which is accomplished by mitosis. ... That occasional 'mutations' occur we know, but there is no ground for supposing that they are similar in nature to those of higher organisms, nor, since they are usually reversible according to conditions, that they play the same part in evolution. We must, in fact, expect that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms. J. Huxley, 1943, Evolution: The Modern Synthesis, New York: Harper & Brothers Publishers, pp. 131–132.

Although it is now clear that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms, this is not because bacteria possess no genes in the sense of accurately quantized portions of hereditary substance.

Max Delbrück (1906–1981)

Source: Wikipedia

Max Ludwig Henning Delbrück, a German–American biophysicist, helped launch the molecular biology research program in the late 1930s. He stimulated physical scientists' interest into biology, especially as to basic research to physically explain genes, mysterious at the time. Formed in 1945 and led by Delbrück along with Salvador Luria and Alfred Hershey, the Phage Group made substantial headway unraveling important aspects of genetics. The three shared the 1969 Nobel Prize in Physiology or Medicine "for their discoveries concerning the replication mechanism and the genetic structure of viruses". He was the first physicist to predict what is now called Delbrück scattering. Delbrück was born in Berlin, German Empire. His mother was granddaughter of Justus von Liebig, eminent chemist, while his father Hans Delbrück was a history professor at the University of Berlin. In 1937, Max left Nazi Germany for America—first California, then Tennessee—becoming a US citizen in 1945.

In 1937, he attained a fellowship from Rockefeller Foundation—which was launching the molecular biology research program—to research genetics of the fruit fly, Drosophila melanogaster, in California Institute of Technology's biology department, where Delbrück could blend interests in biochemistry and genetics. While at Caltech, Delbrück researched bacteria and their viruses (bacteriophages or phages). In 1939, with E.L. Ellis, he coauthored "The growth of bacteriophage", a paper reporting that the viruses reproduce in one step, not exponentially as do cellular organisms. Although Delbrück's Rockefeller Foundation fellowship expired in 1939, the Foundation matched him up with Vanderbilt University in Nashville, Tennessee, where from 1940 to 1947 he taught physics, yet had his laboratory in the biology department. In 1941, Delbrück met Salvador Luria of Indiana University who began visiting Vanderbilt. In 1942, Delbrück and Luria published on bacterial resistance to virus infection mediated by random mutation. Alfred Hershey of Washington University began visiting in 1943. The Luria–Delbrück experiment, also called the Fluctuation Test, demonstrated that Darwin's theory of natural selection acting on random mutations applies to bacteria as well as to more complex organisms. The 1969 Nobel Prize in Physiology or Medicine was awarded to both scientists in part for this work.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Oswald Avery Jr. (1877–1955)

Source: Wikipedia

Oswald Theodore Avery Jr. was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller University Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment (published in 1944 with his co-workers Colin MacLeod and Maclyn McCarty) that isolated DNA as the material of which genes and chromosomes are made. For many years, genetic information was thought to be contained in cell protein. Continuing the research done by Frederick Griffith in 1927, Avery worked with MacLeod and McCarty on the mystery of inheritance. He had received emeritus status from the Rockefeller Institute in 1943, but continued working for five years, though by that time he was in his late sixties. Techniques were available to remove various organic compounds from bacteria, and if the remaining organic compounds were still able to cause R strain bacteria to transform then the substances removed could not be the carrier of genes. S-strain bacteria first had the large cellular structures removed. Then they were treated with protease enzymes, which removed the proteins from the cells before the remainder was placed with R strain bacteria. The R strain bacteria transformed, meaning that proteins did not carry the genes causing the disease. Then the remnants of the R strain bacteria were treated with a deoxyribonuclease enzyme which removed the DNA. After this treatment, the R strain bacteria no longer transformed. This indicated that DNA was the carrier of genes in cells.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Colin Munro MacLeod (1909–1972)

Source: Wikipedia

Colin Munro MacLeod was a Canadian-American geneticist. He was one of a trio of scientists who discovered that deoxyribonucleic acid, or DNA is responsible for the transformation of the physical characteristics of bacteria, which subsequently led to its identification as the molecule responsible for heredity. In his early years as a research scientist, MacLeod, with Oswald Avery and Maclyn McCarty, demonstrated DNA is the molecule responsible for bacterial transformation — and in retrospect, the physical basis of the gene. In 1941, Avery and MacLeod separated a crude extract from smooth (S) strains of Streptococcus pneumoniae, the most common cause of bacterial pneumonia. The S strain extract could convert the more benign rough (R) strains of pneumococci into the disease-causing S form. Later that year, McCarty joined the Avery laboratory, and in 1942, the group began to focus on DNA as the elusive ingredient in the S strain extract as the factor responsible for transformation of R pneumococci into S pneumococci. By early 1943, Avery, MacLeod, and McCarty had shown that DNA was the transforming factor, and in February 1944, published the first of a series of scientific papers in the Journal of Experimental Medicine demonstrating that DNA was the transforming principle. Subsequent experiments confirmed DNA as a universal bearer of genetic information. However, despite the enormous scientific importance of this work, which became known as the Avery–MacLeod–McCarty experiment, the trio did not win a Nobel Prize for their discovery.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Walsh McDermott. 1983. Colin Munro MacLeod, 1909–1972. Biographical Memoirs, National Academy of Sciences.

Maclyn McCarty (1911–2005)

Source: Wikipedia

Maclyn McCarty, who devoted his life as a physician-scientist to studying infectious disease organisms, was best known for his part in the monumental discovery that DNA, rather than protein, constituted the chemical nature of a gene. Uncovering the molecular secret of the gene in question — that for the capsular polysaccharide of pneumococcal bacteria — led the way to studying heredity not only through genetics but also through chemistry, and initiated the dawn of the age of molecular biology. McCarty was the youngest and longest surviving member of the research team responsible for this feat (known as the Avery–MacLeod–McCarty experiment), which also included Oswald T. Avery and Colin MacLeod; he died on January 2, 2005, from congestive heart failure. McCarty was born in 1911 in South Bend, Indiana, the second of four sons of a branch manager for the Studebaker Corporation while it was still a firm for horse-drawn carriages. In his teens, McCarty set himself the goal of becoming a physician-scientist, and he pursued a successful strategy to prepare for admission to, and early success in, Johns Hopkins University Medical School. As an undergraduate at Stanford University, he presciently began his studies in the nascent field of biochemistry, working with James Murray Luck on protein turnover in the liver. In 1937, he began his clinical training in pediatrics at the Harriet Lane Service at Johns Hopkins University. There McCarty developed a special interest in infectious diseases — in particular, antibacterial sulfonamide drug treatments that were just entering medicine — which he subsequently pursued by moving to New York University to work with William Tillett. A National Research Council Fellowship in the medical sciences and an opening in Oswald T. Avery's laboratory spurred his move to Rockefeller University in 1941. At that time, research in the Avery laboratory was focused on the pneumococcal transformation, the heritable alteration of a pneumococcal strain from a nonvirulent rough form to a virulent smooth encapsulated form. McCarty's arrival at the Rockefeller Institute in September 1941 marked 13 years since this discovery, also known as the Griffith phenomenon.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Lederberg, Joshua, and Gotschlich, Emil C. 2005. A Path to Discovery: The Career of Maclyn McCarty. PLoS Biology, 3:e341.

Joshua Lederberg (1925–2008)

Source: Wikipedia

Joshua Lederberg was an American molecular biologist known for his work in microbial genetics, artificial intelligence, and the United States space program. He was 33 years old when he won the 1958 Nobel Prize in Physiology or Medicine for discovering that bacteria can mate and exchange genes (bacterial conjugation). He shared the prize with Edward Tatum and George Beadle, who won for their work with genetics. He enrolled in Columbia University in 1941, majoring in zoology. Under the mentorship of Francis J. Ryan, he conducted biochemical and genetic studies on the bread mold Neurospora crassa. Intending to receive his MD and fulfill his military service obligations, Lederberg worked as a hospital corpsman during 1943 in the clinical pathology laboratory at St. Albans Naval Hospital, where he examined sailors' blood and stool samples for malaria. He went on to receive his undergraduate degree in 1944.

Joshua Lederberg began medical studies at Columbia's College of Physicians and Surgeons while continuing to perform experiments. Inspired by Oswald Avery's discovery of the importance of DNA, Lederberg began to investigate his hypothesis that, contrary to prevailing opinion, bacteria did not simply pass down exact copies of genetic information, making all cells in a lineage essentially clones. After making little progress at Columbia, Lederberg wrote to Edward Tatum, Ryan's post-doctoral mentor, proposing a collaboration. In 1946 and 1947, Lederberg took a leave of absence to study under the mentorship of Tatum at Yale University. Lederberg and Tatum showed that the bacterium Escherichia coli entered a sexual phase during which it could share genetic information through bacterial conjugation. With this discovery and some mapping of the E. coli chromosome, Lederberg was able to receive his Ph.D. from Yale University in 1947. Instead of returning to Columbia to finish his medical degree, Lederberg chose to accept an offer of an assistant professorship in genetics at the University of Wisconsin–Madison. In 1951, Lederberg and Norton Zinder showed that genetic material could be transferred from one strain of the bacterium Salmonella typhimurium to another using viral material as an intermediary step. This process is called transduction.

In 1958, Joshua Lederberg received the Nobel Prize and moved to Stanford University, where he was the founder and chairman of the Department of Genetics. In 1978, he became the president of Rockefeller University, until he stepped down in 1990 and became professor-emeritus of molecular genetics and informatics at Rockefeller University, considering his extensive research and publications in these disciplines. Throughout his career, Lederberg was active as a scientific advisor to the U.S. government.

See Also:

Walter Bodmer and Ann Ganesan. 2011. Joshua Lederberg. 23 May 1925 – 2 February 2008. Biographical Memoirs of Fellows of the Royal Society. 57: 229–251. doi:10.1098/rsbm.2010.0024

Joshua Lederberg Papers 1904-2008

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

S. Gaylen Bradley. 2009. Joshua Lederberg 1925 – 2008. National Academy of Sciences, Biographical Memoirs

Edward Tatum (1909–1975)

Source: Wikipedia

Edward Lawrie Tatum was an American geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Beadle for showing that genes control individual steps in metabolism. The other half of that year's award went to Joshua Lederberg. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments, published in 1941, led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. This became a fundamental concept in physiological genetics. Tatum went on to study genetics in bacteria. An active area of research in his laboratory was to understand the basis of Tryptophan biosynthesis in Escherichia coli. Later, Tatum and his student Joshua Lederberg showed that E. coli could share genetic information through recombination. This became a fundamental concept in microbial genetics.

See Also:

Joshua Lederberg. 1990. Edward Lawrie Tatum 1909 – 1975. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Raphael Weldon (1860–1906)

Source: Wikipedia

Walter Frank Raphael Weldon, generally called Raphael Weldon, was an English evolutionary biologist and a founder of biometry. He was the joint founding editor of Biometrika, with Francis Galton and Karl Pearson. Medicine was his intended career and he spent the academic year 1876-1877 at University College London. Among his teachers were the zoologist E. Ray Lankester and the mathematician Olaus Henrici. In the following year he transferred to King's College London and then to St John's College, Cambridge in 1878. There Weldon studied with the developmental morphologist Francis Balfour who influenced him greatly; Weldon gave up his plans for a career in medicine. In 1881 he gained a first-class honours degree in the Natural Science Tripos; in the autumn he left for the Naples Zoological Station to begin the first of his studies on marine biological organisms.

Upon returning to Cambridge in 1882, he was appointed university lecturer in Invertebrate Morphology. Weldon's work was centred on the development of a fuller understanding of marine biological phenomena and selective death rates of these organisms. In 1889 Weldon succeeded Lankester in the Jodrell Chair of Zoology at University College London, and was elected to the Royal Society in 1890. Royal Society records show his election supporters included the great zoologists of the day: Huxley, Lankester, Poulton, Newton, Flower, Romanes and others. His interests were changing from morphology to problems in variation and organic correlation. He began using the statistical techniques that Francis Galton had developed for he had come to the view that "the problem of animal evolution is essentially a statistical problem." Weldon began working with his University College colleague, the mathematician Karl Pearson. Their partnership was very important to both men and survived Weldon's move to the Linacre Chair of Zoology at Oxford University in 1899. In the years of their collaboration Pearson laid the foundations of modern statistics.

In 1900 the work of Gregor Mendel was rediscovered and this precipitated a conflict between Weldon and Pearson on the one side and William Bateson on the other. Bateson, who had been taught by Weldon, took a very strong line against the biometricians. This bitter dispute ranged across substantive issues of the nature of evolution and methodological issues such as the value of the statistical method. In The Origins of Theoretical Population Genetics, William Provine gives a detailed account of the controversy. The debate lost much of its intensity with the death of Weldon in 1906, though the general debate between the biometricians and the Mendelians continued until the creation of the modern evolutionary synthesis in the 1930s.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Online Weldon Biography

Weldon, Walter Frank Raphael. Encyclopedia of Mathematics

P Froggatt and N C Nevin. 1971. The 'law of ancestral heredity' and the Mendelian-ancestrian controversy in England, 1889-1906. Journal of Medical Genetics, 8:1-36.

Weldon, W. F. R. 1902. Mendel's laws of alternative inheritance in peas. Biometrika, 1:228-254.

Karl Pearson. 1906. "Walter Frank Raphael Weldon 1860-1906," Biometrika, 5:1-52.

Godfrey Harold Hardy (1877–1947)

Source: Wikipedia

Godfrey Harold "G. H." Hardy was an English mathematician, known for his achievements in number theory and mathematical analysis. In addition to his research, Hardy is remembered for his 1940 essay on the aesthetics of mathematics, entitled A Mathematician's Apology. He was the mentor of the Indian mathematician Srinivasa Ramanujan.

Although every geneticist has heard of the Hardy-Weinberg Law and of Hardy-Weinberg Equilibrium, and although nearly all basic biology texts teach that G. H. Hardy played a seminal role in founding population genetics, most biologists don't realize that Hardy's total contribution to biology consisted of a single one-page letter to the editor in Science.

The letter began,

I am reluctant to intrude in a discussion concerning matters of which I have no expert knowledge, and I should have expected the very simple point which I wish to make to have been familiar to biologists. However, some remarks of Mr. Udny Yule, to which Mr. R. C. Punnett has called my attention, suggest that it may still be worth making.

With that, Hardy offered his "simple point" and then washed his hands of biology. His autobiography, A Mathematician's Apology, makes no mention of population genetics. Mathematically, Hardy's "very simple point" was the trivial assertion that (p + q)² = p² + 2pq + q² Biologically, however, Hardy's point was of greater consequence, as his simple algebra implied that Mendelian mechanisms, acting alone, have no effect upon allele frequencies in a population — an observation that was far from obvious to most biologists.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Wilhelm Weinberg (1862–1937)

Source: Wikipedia

Dr Wilhelm Weinberg was a German obstetrician-gynecologist, practicing in Stuttgart, who in a 1908 paper, published in German in Jahresheft des Vereins für vaterländische Naturkunde in Württemberg (The Annals of the Society of National Natural History in Württemberg), expressed the concept that would later come to be known as the Hardy-Weinberg principle. Weinberg is also credited as the first to explain the effect of ascertainment bias on observations in genetics. Weinberg developed the principle of genetic equilibrium independently of British mathematician G.H. Hardy. He delivered an exposition of his ideas in a lecture on January 13, 1908, before the Verein für vaterländische Naturkunde in Württemberg (Society for the Natural History of the Fatherland in Württemberg), about six months before Hardy's paper was published in English. His lecture was printed later that year in the society's yearbook. Weinberg's contributions were unrecognized in the English speaking world for more than 35 years. Curt Stern, a German scientist who immigrated to the United States before World War II, pointed out in a brief paper in Science that Weinberg's exposition was both earlier and more comprehensive than Hardy's. Before 1943, the concepts in genetic equilibrium that are known today as the Hardy-Weinberg principle had been known as "Hardy's law" or "Hardy's formula" in English-language texts.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

John Burton Sanderson Haldane (1892–1964)

Source: Wikipedia

John Burdon Sanderson Haldane was a British-born scientist known for his work in the study of physiology, genetics, evolutionary biology, and in mathematics, where he made innovative contributions to the fields of statistics and biostatistics. He was the son of the equally famous John Scott Haldane and was a professed socialist, Marxist, atheist, and humanist whose political dissent led him to leave England in 1956 and live in India, becoming a naturalised Indian citizen in 1961. His first paper in 1915 demonstrated genetic linkage in mammals while subsequent works helped to create population genetics, thus establishing a unification of Mendelian genetics and Darwinian evolution by natural selection whilst laying the groundwork for modern evolutionary synthesis.

He was one of the three major figures to develop the mathematical theory of population genetics, along with Ronald Fisher and Sewall Wright. Thusly he played an important role in the modern evolutionary synthesis, which is popularly called "neo-Darwinism", as in Richard Dawkins' 1976 work titled The Selfish Gene. He re-established natural selection as the premier mechanism of evolution by explaining it in terms of the mathematical consequences of Mendelian inheritance. He wrote a series of ten papers called A Mathematical Theory of Natural and Artificial Selection, on the numerical formalism underpinning natural selection. It showed that gene frequencies have direction and rates of change; and he pioneered the interaction of natural selection with mutation and animal migration. Haldane's book, The Causes of Evolution (1932), summarised these results, especially in its extensive appendix.

Arthur C. Clarke credited him as "perhaps the most brilliant science populariser of his generation". Nobel laureate Peter Medawar called Haldane "the cleverest man I ever knew".

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

William E. Castle (1867–1962)

Source: Wikipedia

William Ernest Castle was born on a farm in Ohio and took an early interest in natural history. He graduated in 1889 from Denison University in Granville, Ohio, a Baptist college that emphasized classics, and went on to become a teacher of Latin at Ottawa University in Ottawa, Kansas, where he published his first paper on the flowering plants of the area. After three years of teaching, botany won out over Latin. Castle entered the senior class of Harvard University in 1892 and in 1893 took a second A.B. degree with honors. He was appointed laboratory assistant in zoology, an A.M. degree in 1894 and a Ph.D. in 1895. He then taught zoology at the University of Wisconsin–Madison and at the Knox College in Galesburg, Illinois, each for a year.

Castle returned to Harvard in 1897. His early work focused on embryology, but after the rediscovery of Mendelian genetics in 1900, he turned to mammalian genetics, especially that of the guinea pig. At Harvard, Charles W. Woodworth suggested to him that Drosophila might be used for genetical work. Castle was the first to use the fruit fly Drosophila melanogaster, and it was his work that inspired T. H. Morgan to use Drosophila and the basis of Morgan's 1933 Nobel Prize. In 1908 Castle moved from the Harvard Museum of Comparative Zoology to the Bussey Institution for Applied Biology. There his most famous PhD student was Sewall Wright who graduated in 1915. The same year he was elected to membership in the U.S. National Academy of Sciences. When the Eugenics Record Office was founded in 1912, he served as a member of its scientific advisory board, and in 1916 he was one of the 10 founders of the scientific journal Genetics.

See Also:

Dunn, L. C. 1965. William Ernest Castle 1867 – 1962. Biographical Memoirs, National Academy of Sciences.

Castle, W. E. 1911. Heredity in Relation to Evolution and Animal Breeding. New York: D. Appleton and Company. 184 pp.

William E. Castle Papers. American Philosophical Society.

Ronald Aylmer Fisher (1890–1962)

Source: Wikipedia

Sir Ronald Aylmer Fisher, who published as R. A. Fisher, was an English statistician and biologist who used mathematics to combine Mendelian genetics and natural selection. This contributed to the revival of Darwinism in the early 20th century revision of the theory of evolution known as the modern synthesis. He was a prominent eugenicist in the early part of his life. In 1918 he published The Correlation Between Relatives on the Supposition of Mendelian Inheritance in 1918, in which he simultaneously resolved one of the outstanding debates in biology (the biometricians vs. the Mendelians) and introduced the idea of the analysis of variance. This paper was originally submitted to Biometrika where it was rejected, with a biological reviewer allowing that perhaps the mathematics had some value, but the biology was inconsequential while a statistical reviewer held the converse view. In 1925 he published Statistical Methods for Research Workers, one of the 20th century's most influential books on statistical methods. Fisher's method is a technique for data fusion or "meta-analysis" (analysis of analyses). This book also popularized the p-value, and it plays a central role in his approach. Fisher proposes the level p = 0.05, or a 1 in 20 chance of being exceeded by chance, as a limit for statistical significance, and applies this to a normal distribution (as a two-tailed test), thus yielding the rule of two standard deviations (on a normal distribution) for statistical significance. In 1933 he became Professor of Eugenics at University College London until 1939 when the department was dissolved. In 1935, he published by The Design of Experiments, which was also fundamental, [and promoted] statistical technique and application. In this book Fisher also outlined the Lady tasting tea, now a famous design of a statistical randomized experiment which uses Fisher's exact test and is the original exposition of Fisher's notion of a null hypothesis. In 1936 he published Has Mendel's Work Been Rediscovered?, in which he suggested that Mendel's results were too good to be true and that someone (perhaps an over-eager assistant) had fudged the results.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Sewall Wright (1889–1988)

Source: Wikipedia

Sewall Green Wright was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongside Ronald Fisher and J.B.S. Haldane, which was a major step in the development of the modern evolutionary synthesis combining genetics with evolution. He discovered the inbreeding coefficient and methods of computing it in pedigree animals. He extended this work to populations, computing the amount of inbreeding between members of populations as a result of random genetic drift, and along with Fisher he pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection, mutation, migration and genetic drift. Wright also made major contributions to mammalian and biochemical genetics. His papers on inbreeding, mating systems, and genetic drift make him a principal founder of theoretical population genetics, along with R. A. Fisher and J. B. S. Haldane. Their theoretical work is the origin of the modern evolutionary synthesis or neodarwinian synthesis. Wright was the inventor/discoverer of the inbreeding coefficient and F-statistics, standard tools in population genetics. He was the chief developer of the mathematical theory of genetic drift, which is sometimes known as the Sewall Wright effect, cumulative stochastic changes in gene frequencies that arise from random births, deaths, and Mendelian segregations in reproduction. In this work he also introduced the concept of effective population size. Wright was convinced that the interaction of genetic drift and the other evolutionary forces was important in the process of adaptation. He described the relationship between genotype or phenotype and fitness as fitness surfaces or evolutionary landscapes. On these landscapes mean population fitness was the height, plotted against horizontal axes representing the allele frequencies or the average phenotypes of the population. Natural selection would lead to a population climbing the nearest peak, while genetic drift would cause random wandering.

See Also:

Excellent book: William B. Provine. The Origins of Theoretical Population Genetics

Ching Chun Li (1912–2003)

Source: Wikipedia

Ching Chun Li was a respected American population geneticist and human geneticist. Li was best known for his book An Introduction to Population Genetics and his teaching in human genetics. Ching Chun Li was born on October 27, 1912, in Taku, Tianjin, China. He received his BS degree in agronomy from the University of Nanking in 1936 and a PhD in plant breeding and genetics from Cornell University in 1940. He worked as post-doctorate fellows at Columbia University and North Carolina State University from 1940 to 1941. Li returned to China at the age of 30 and became the Professor of Genetics and Biometry at University of Nanking, his alma mater, in 1943. After World War II, he moved to Beijing for a Professorship of Agronomy at Peking University in 1946, where he finished An Introduction to Population Genetics in 1948. The book was the first notable publication where the population-genetics ideas of Ronald Fisher, Sewall Wright, and J. B. S. Haldane were brought together, synthesized, and presented in a coherent and readily understood manner.

See Also:

Aravinda Chakravarti. 2004. Ching Chun Li (1912–2003): A Personal Remembrance of a Hero of Genetics. The American Journal of Human Genetics, 74:789-792.

Eliot B. Spiess. 2005. Remembrance of Ching Chun Li, 1912–2003. Genetics, 169:9-11.

Friedrich Miescher (1844–1895)

Source: Wikipedia

Johannes Friedrich Miescher was a Swiss physician and biologist. He was the first researcher to isolate nucleic acid. Miescher isolated various phosphate-rich chemicals, which he called nuclein (now nucleic acids), from the nuclei of white blood cells in 1869 in Felix Hoppe-Seyler's laboratory at the University of Tübingen, Germany, paving the way for the identification of DNA as the carrier of inheritance. The significance of the discovery, first published in 1871, was not at first apparent, and it was Albrecht Kossel who made the initial inquiries into its chemical structure. Later, Friedrich Miescher raised the idea that the nucleic acids could be involved in heredity.

See Also:

Ralf Dahm. 2008. Discovering DNA: Friedrich Miescher and the early years of nucleic acid research. Human Genetics, 122:565. doi:10.1007/s00439-007-0433-0

Hermann Joseph Muller (1890–1967)

Source: Wikipedia

Hermann Joseph Muller (or H. J. Muller) was an American geneticist, educator, and Nobel laureate best known for his work on the physiological and genetic effects of radiation (Mutagenesis) as well as his outspoken political beliefs. Muller frequently warned of the long-term dangers of radioactive fallout from nuclear war and nuclear testing, helping to raise public awareness in this area. At 16 he entered Columbia College. From his first semester he was interested in biology; he became an early convert of the Mendelian-chromosome theory of heredity — and the concept of genetic mutations and natural selection as the basis for evolution. Muller remained at Columbia (the pre-eminent American zoology program at the time, thanks to E. B. Wilson and his students) for graduate school. He became interested in the Drosophila genetics work of Thomas Hunt Morgan's fly lab after undergraduate bottle washers Alfred Sturtevant and Calvin Bridges joined his Biology Club. He joined Morgan's group in 1912 (after two years of informal participation). In 1918, he proposed an explanation for the dramatic discontinuous alterations in Oenothera larmarckiana that were the basis of Hugo de Vries's theory of mutationism: "balanced lethals" allowed the accumulation of recessive mutations, and rare crossing over events resulted in the sudden expression of these hidden traits. In other words, de Vries's experiments were explainable by the Mendelian-chromosome theory.

Frederick Griffith (1879–1941)

Source: Wikipedia

Frederick Griffith was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function. He showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. The observation was attributed to an unidentified transforming principle or transforming factor. This was later identified as DNA. America's leading pneumococcal researcher, Oswald T. Avery, speculated that Griffith had failed to apply adequate controls. A cautious and thorough researcher, and a reticent individual, Griffith's tendency was to publish only findings that he believed truly significant, and Griffith's findings were rapidly confirmed by researchers in Avery's laboratory. His discovery was one of the first to show the central role of DNA in heredity.

Griffith's experiment showed that one strain, R (rough, non-virulent) of bacteria could be transformed to exhibit the attributes of a different strain S (smooth, virulent),through exposure to material from dead members of the other strain. Specifically, he found that if he injected live R bacteria into mice, the mice lived (no surprise, R bacteria are non-virulent). He also found that if he injected deda S bacteria into mice, the mice lived (again, no surprise, dead bacteria do not cause disease). However, if he injected mice with a combination of live R and dead S, the mice died from an infection of live S bacteria. It appeared that exposure to dead S bacteria had transformed live R into live S bacteria.

This stunning result seemed to prove that there was some non-living, physical basis to bacteria hereditary — some molecular carrier of genetic information — that was being lost from the dead S bacteria and picked up by the live R bacteria, allowing the R to transform into S. Now the question became, What is the nature of that hereditary molecule?

In 1944, work by Oswald Avery, Colin MacLeod, and Maclyn McCarty, showed that DNA is the substance that causes bacterial transformation.

See Also:

Griffith's Experiment, Explained

The Avery–MacLeod–McCarty experiment

Salvador Luria (1912–1991)

Source: Wikipedia

Salvador Edward Luria was an Italian microbiologist, later a naturalized U.S. citizen. He won the Nobel Prize in Physiology or Medicine in 1969, with Max Delbrück and Alfred Hershey, for their discoveries on the replication mechanism and the genetic structure of viruses. Salvador Luria also showed that bacterial resistance to viruses (phages) is genetically inherited. Luria was born Salvatore Edoardo Luria, in Turin, Italy to an influential Italian Sephardi Jewish family. His parents were Ester (Sacerdote) and Davide Luria. He attended the medical school at the University of Turin studying with Giuseppe Levi. There, he met two other future Nobel laureates: Rita Levi-Montalcini and Renato Dulbecco. He graduated from the University of Turin in 1935. From 1936 to 1937, Luria served his required time in the Italian army as a medical officer. He then took classes in radiology at the University of Rome. Here, he was introduced to Max Delbrück's theories on the gene as a molecule and began to formulate methods for testing genetic theory with the bacteriophages, viruses that infect bacteria. In 1938, he received a fellowship to study in the United States, where he intended to work with Delbrück. Soon after Luria received the award, Benito Mussolini's fascist regime banned Jews from academic research fellowships. Without funding sources for work in the U.S. or Italy, Luria left his home country for Paris, France in 1938. As the Nazi German armies invaded France in 1940, Luria fled on bicycle to Marseille where he received an immigration visa to the United States.

Luria arrived in New York City on September 12, 1940, and soon changed his first and middle names. With the help of physicist Enrico Fermi, whom he knew from his time at the University of Rome, Luria received a Rockefeller Foundation fellowship at Columbia University. He soon met Delbrück and Hershey, and they collaborated on experiments at Cold Spring Harbor Laboratory and in Delbrück's lab at Vanderbilt University. His famous experiment with Delbrück in 1943, known as the Luria–Delbrück experiment, demonstrated statistically that inheritance in bacteria must follow Darwinian rather than Lamarckian principles and that mutant bacteria occurring randomly can still bestow viral resistance without the virus being present. The idea that natural selection affects bacteria has profound consequences, for example, it explains how bacteria develop antibiotic resistance. From 1943 to 1950, he worked at Indiana University. His first graduate student was James D. Watson, who went on to discover the structure of DNA with Francis Crick. In January 1947, Luria became a naturalized citizen of the United States.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Max Delbrück (1906–1981)

Source: Wikipedia

Max Ludwig Henning Delbrück, a German–American biophysicist, helped launch the molecular biology research program in the late 1930s. He stimulated physical scientists' interest into biology, especially as to basic research to physically explain genes, mysterious at the time. Formed in 1945 and led by Delbrück along with Salvador Luria and Alfred Hershey, the Phage Group made substantial headway unraveling important aspects of genetics. The three shared the 1969 Nobel Prize in Physiology or Medicine "for their discoveries concerning the replication mechanism and the genetic structure of viruses". He was the first physicist to predict what is now called Delbrück scattering. Delbrück was born in Berlin, German Empire. His mother was granddaughter of Justus von Liebig, eminent chemist, while his father Hans Delbrück was a history professor at the University of Berlin. In 1937, Max left Nazi Germany for America—first California, then Tennessee—becoming a US citizen in 1945.

In 1937, he attained a fellowship from Rockefeller Foundation—which was launching the molecular biology research program—to research genetics of the fruit fly, Drosophila melanogaster, in California Institute of Technology's biology department, where Delbrück could blend interests in biochemistry and genetics. While at Caltech, Delbrück researched bacteria and their viruses (bacteriophages or phages). In 1939, with E.L. Ellis, he coauthored "The growth of bacteriophage", a paper reporting that the viruses reproduce in one step, not exponentially as do cellular organisms. Although Delbrück's Rockefeller Foundation fellowship expired in 1939, the Foundation matched him up with Vanderbilt University in Nashville, Tennessee, where from 1940 to 1947 he taught physics, yet had his laboratory in the biology department. In 1941, Delbrück met Salvador Luria of Indiana University who began visiting Vanderbilt. In 1942, Delbrück and Luria published on bacterial resistance to virus infection mediated by random mutation. Alfred Hershey of Washington University began visiting in 1943. The Luria–Delbrück experiment, also called the Fluctuation Test, demonstrated that Darwin's theory of natural selection acting on random mutations applies to bacteria as well as to more complex organisms. The 1969 Nobel Prize in Physiology or Medicine was awarded to both scientists in part for this work.

See Also:

Luria, S. E., and Delbrück, M. 1943. Mutations of bacteria from virus sensitivity to virus resistance. Genetics, 28:491-511.

Erwin Schrödinger (1887–1961)

Source: Wikipedia

Erwin Rudolf Josef Alexander Schrödinger, was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in the field of quantum theory, which formed the basis of wave mechanics: he formulated the wave equation (stationary and time-dependent Schrödinger equation) and revealed the identity of his development of the formalism and matrix mechanics. Schrödinger proposed an original interpretation of the physical meaning of the wave function. In addition, he was the author of many works in various fields of physics: statistical mechanics and thermodynamics, physics of dielectrics, colour theory, electrodynamics, general relativity, and cosmology, and he made several attempts to construct a unified field theory. In his 1944 book What Is Life? Schrödinger addressed the problems of genetics, looking at the phenomenon of life from the point of view of physics.

In the book, Schrödinger introduced the paradoxical idea of an aperiodic crystal that contained genetic information in its configuration of covalent chemical bonds. [The idea of an aperiodic crystal bears a passing resemblance to the notion of dehydrated water.] In the book, Schrödinger specifically discussed the likelihood that hereditary information is somehow encoded in the molecular structure of chromosomes, noting:

It is these chromosomes, or probably only an axial skeleton fibre of what we actually see under the microscope as the chromosome, that contain in some kind of code-script the entire pattern of the individual's future development and of its functioning in the mature state. Every complete set of chromosomes contains the full code; so there are, as a rule, two copies of the latter in the fertilized egg cell, which forms the earliest stage of the future individual. In calling the structure of the chromosome fibres a code-script we mean that the all-penetrating mind, once conceived by Laplace, to which every causal connection lay immediately open, could tell from their structure whether the egg would develop, under suitable conditions, into a black cock or into a speckled hen, into a fly or a maize plant, a rhododendron, a beetle, a mouse or a woman.

In retrospect, Schrödinger's aperiodic crystal can be viewed as a well-reasoned theoretical prediction of what biologists should have been looking for during their search for genetic material. Both James D. Watson, and independently, Francis Crick, co-discoverers of the structure of DNA, credited Schrödinger's book with presenting an early theoretical description of how the storage of genetic information would work, and each respectively acknowledged the book as a source of inspiration for their initial researches. These ideas provide the conceptual foundation of molecular genetics. Schrödinger paid great attention to the philosophical aspects of science, ancient and oriental philosophical concepts, ethics, and religion. He also wrote on philosophy and theoretical biology. He is also known for his Schrödinger's cat thought-experiment.

Oswald Avery Jr. (1877–1955)

Source: Wikipedia

Oswald Theodore Avery Jr. was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller University Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment (published in 1944 with his co-workers Colin MacLeod and Maclyn McCarty) that isolated DNA as the material of which genes and chromosomes are made. For many years, genetic information was thought to be contained in cell protein. Continuing the research done by Frederick Griffith in 1927, Avery worked with MacLeod and McCarty on the mystery of inheritance. He had received emeritus status from the Rockefeller Institute in 1943, but continued working for five years, though by that time he was in his late sixties. Techniques were available to remove various organic compounds from bacteria, and if the remaining organic compounds were still able to cause R strain bacteria to transform then the substances removed could not be the carrier of genes. S-strain bacteria first had the large cellular structures removed. Then they were treated with protease enzymes, which removed the proteins from the cells before the remainder was placed with R strain bacteria. The R strain bacteria transformed, meaning that proteins did not carry the genes causing the disease. Then the remnants of the R strain bacteria were treated with a deoxyribonuclease enzyme which removed the DNA. After this treatment, the R strain bacteria no longer transformed. This indicated that DNA was the carrier of genes in cells.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Colin Munro MacLeod (1909–1972)

Source: Wikipedia

Colin Munro MacLeod was a Canadian-American geneticist. He was one of a trio of scientists who discovered that deoxyribonucleic acid, or DNA is responsible for the transformation of the physical characteristics of bacteria, which subsequently led to its identification as the molecule responsible for heredity. In his early years as a research scientist, MacLeod, with Oswald Avery and Maclyn McCarty, demonstrated DNA is the molecule responsible for bacterial transformation — and in retrospect, the physical basis of the gene. In 1941, Avery and MacLeod separated a crude extract from smooth (S) strains of Streptococcus pneumoniae, the most common cause of bacterial pneumonia. The S strain extract could convert the more benign rough (R) strains of pneumococci into the disease-causing S form. Later that year, McCarty joined the Avery laboratory, and in 1942, the group began to focus on DNA as the elusive ingredient in the S strain extract as the factor responsible for transformation of R pneumococci into S pneumococci. By early 1943, Avery, MacLeod, and McCarty had shown that DNA was the transforming factor, and in February 1944, published the first of a series of scientific papers in the Journal of Experimental Medicine demonstrating that DNA was the transforming principle. Subsequent experiments confirmed DNA as a universal bearer of genetic information. However, despite the enormous scientific importance of this work, which became known as the Avery–MacLeod–McCarty experiment, the trio did not win a Nobel Prize for their discovery.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Walsh McDermott. 1983. Colin Munro MacLeod, 1909–1972. Biographical Memoirs, National Academy of Sciences.

Maclyn McCarty (1911–2005)

Source: Wikipedia

Maclyn McCarty, who devoted his life as a physician-scientist to studying infectious disease organisms, was best known for his part in the monumental discovery that DNA, rather than protein, constituted the chemical nature of a gene. Uncovering the molecular secret of the gene in question — that for the capsular polysaccharide of pneumococcal bacteria — led the way to studying heredity not only through genetics but also through chemistry, and initiated the dawn of the age of molecular biology. McCarty was the youngest and longest surviving member of the research team responsible for this feat (known as the Avery–MacLeod–McCarty experiment), which also included Oswald T. Avery and Colin MacLeod; he died on January 2, 2005, from congestive heart failure. McCarty was born in 1911 in South Bend, Indiana, the second of four sons of a branch manager for the Studebaker Corporation while it was still a firm for horse-drawn carriages. In his teens, McCarty set himself the goal of becoming a physician-scientist, and he pursued a successful strategy to prepare for admission to, and early success in, Johns Hopkins University Medical School. As an undergraduate at Stanford University, he presciently began his studies in the nascent field of biochemistry, working with James Murray Luck on protein turnover in the liver. In 1937, he began his clinical training in pediatrics at the Harriet Lane Service at Johns Hopkins University. There McCarty developed a special interest in infectious diseases — in particular, antibacterial sulfonamide drug treatments that were just entering medicine — which he subsequently pursued by moving to New York University to work with William Tillett. A National Research Council Fellowship in the medical sciences and an opening in Oswald T. Avery's laboratory spurred his move to Rockefeller University in 1941. At that time, research in the Avery laboratory was focused on the pneumococcal transformation, the heritable alteration of a pneumococcal strain from a nonvirulent rough form to a virulent smooth encapsulated form. McCarty's arrival at the Rockefeller Institute in September 1941 marked 13 years since this discovery, also known as the Griffith phenomenon.

See Also:

The Avery–MacLeod–McCarty Experiment

The original paper describing the Avery–MacLeod–McCarty Experiment

Lederberg, Joshua. 1994. The transformation of genetics by DNA: An anniversary celebration of Avery, MacLeod and McCarty (1944). Genetics. 136:423-426.

Lederberg, Joshua, and Gotschlich, Emil C. 2005. A Path to Discovery: The Career of Maclyn McCarty. PLoS Biology, 3:e341.

Joshua Lederberg (1925–2008)

Source: Wikipedia

Joshua Lederberg was an American molecular biologist known for his work in microbial genetics, artificial intelligence, and the United States space program. He was 33 years old when he won the 1958 Nobel Prize in Physiology or Medicine for discovering that bacteria can mate and exchange genes (bacterial conjugation). He shared the prize with Edward Tatum and George Beadle, who won for their work with genetics. He enrolled in Columbia University in 1941, majoring in zoology. Under the mentorship of Francis J. Ryan, he conducted biochemical and genetic studies on the bread mold Neurospora crassa. Intending to receive his MD and fulfill his military service obligations, Lederberg worked as a hospital corpsman during 1943 in the clinical pathology laboratory at St. Albans Naval Hospital, where he examined sailors' blood and stool samples for malaria. He went on to receive his undergraduate degree in 1944.

Joshua Lederberg began medical studies at Columbia's College of Physicians and Surgeons while continuing to perform experiments. Inspired by Oswald Avery's discovery of the importance of DNA, Lederberg began to investigate his hypothesis that, contrary to prevailing opinion, bacteria did not simply pass down exact copies of genetic information, making all cells in a lineage essentially clones. After making little progress at Columbia, Lederberg wrote to Edward Tatum, Ryan's post-doctoral mentor, proposing a collaboration. In 1946 and 1947, Lederberg took a leave of absence to study under the mentorship of Tatum at Yale University. Lederberg and Tatum showed that the bacterium Escherichia coli entered a sexual phase during which it could share genetic information through bacterial conjugation. With this discovery and some mapping of the E. coli chromosome, Lederberg was able to receive his Ph.D. from Yale University in 1947. Instead of returning to Columbia to finish his medical degree, Lederberg chose to accept an offer of an assistant professorship in genetics at the University of Wisconsin–Madison. In 1951, Lederberg and Norton Zinder showed that genetic material could be transferred from one strain of the bacterium Salmonella typhimurium to another using viral material as an intermediary step. This process is called transduction.

In 1958, Joshua Lederberg received the Nobel Prize and moved to Stanford University, where he was the founder and chairman of the Department of Genetics. In 1978, he became the president of Rockefeller University, until he stepped down in 1990 and became professor-emeritus of molecular genetics and informatics at Rockefeller University, considering his extensive research and publications in these disciplines. Throughout his career, Lederberg was active as a scientific advisor to the U.S. government.

See Also:

Walter Bodmer and Ann Ganesan. 2011. Joshua Lederberg. 23 May 1925 – 2 February 2008. Biographical Memoirs of Fellows of the Royal Society. 57: 229–251. doi:10.1098/rsbm.2010.0024

Joshua Lederberg Papers 1904-2008

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

S. Gaylen Bradley. 2009. Joshua Lederberg 1925 – 2008. National Academy of Sciences, Biographical Memoirs

Edward Tatum (1909–1975)

Source: Wikipedia

Edward Lawrie Tatum was an American geneticist. He shared half of the Nobel Prize in Physiology or Medicine in 1958 with George Beadle for showing that genes control individual steps in metabolism. The other half of that year's award went to Joshua Lederberg. Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations. In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways. These experiments, published in 1941, led them to propose a direct link between genes and enzymatic reactions, known as the one gene, one enzyme hypothesis. This became a fundamental concept in physiological genetics. Tatum went on to study genetics in bacteria. An active area of research in his laboratory was to understand the basis of Tryptophan biosynthesis in Escherichia coli. Later, Tatum and his student Joshua Lederberg showed that E. coli could share genetic information through recombination. This became a fundamental concept in microbial genetics.

See Also:

Joshua Lederberg. 1990. Edward Lawrie Tatum 1909 – 1975. National Academy of Sciences, Biographical Memoirs

The Nobel Prize in Physiology or Medicine 1958 was divided, one half jointly to George Wells Beadle and Edward Lawrie Tatum for their discovery that genes act by regulating definite chemical events and the other half to Joshua Lederberg for his discoveries concerning genetic recombination and the organization of the genetic material of bacteria.

Beadle, GW and Tatum, EL. 1941. Genetic Control of Biochemical Reactions in Neurospora. Proceedings of the National Academy of Sciences U S A. 27: 499–506.

Chhetri, Divyash, ""Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum". Embryo Project Encyclopedia (2014-06-11). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/7900.

Erwin Chargaff (1905–2002)

Source: Wikipedia

Erwin Chargaff (11 August 1905 – 20 June 2002) was an Austro-Hungarian biochemist that immigrated to the United States during the Nazi era and was a professor of biochemistry at Columbia University medical school. Through careful experimentation, Chargaff made two observations that helped to disprove the tetranucleotide model of DNA. Under the tetranucleotide hypothesis, it was assumed that DNA was built as a simple repeating polymer of units consisting of one adenine, one thymine, one cytosine, and one guanine. Such a structure would mean that all DNA molecules has essentially the same structure, differeing only in length. Such a molecule would be incapable of carrying hereditary information. Chargaff's observations: (1) the percent nucleotide composition of DNA was not exactly 25% of each nucleotide, (2) the percent nucleotide composition of DNA differed (slightly) from one species to another, and (3) the percent nucleotide composition of DNA was constant within a species. He also observed regular numerical patterns in the nucleotide makeup of any DNA sample. The two best remembered patterns are that, in any DNA sample, the amount of adenine always equals the amount of thymine, and the amount of guanine always equals the amount of cytosine. These observations, especially the A-T and C-G equalities, helped Watson and Crick devise the double-helix model of DNA. Chargaff had a quick wit and a sharp pen and he was not impressed with advances made through theory rather than through laboratory work. He once commented that Molecular biology is essentially the practice of biochemistry without a license.

James Dewey Watson (1928–      )

Source: Wikipedia

James Dewey Watson is an American molecular biologist, geneticist and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick. Watson, Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". From 1956 to 1976, Watson was on the faculty of the Harvard University Biology Department, promoting research in molecular biology. From 1968 he served as director of Cold Spring Harbor Laboratory (CSHL), greatly expanding its level of funding and research. At CSHL, he shifted his research emphasis to the study of cancer, along with making it a world leading research center in molecular biology. In 1994, he started as president and served for 10 years. He was then appointed chancellor, serving until he resigned in 2007. Between 1988 and 1992, Watson was associated with the National Institutes of Health, helping to establish the Human Genome Project.

Francis Crick (1916–2004)

Source: Wikipedia

Francis Harry Compton Crick was a British molecular biologist, biophysicist, and neuroscientist, most noted for being a co-discoverer of the structure of the DNA molecule in 1953 with James Watson. Together with Watson and Maurice Wilkins, he was jointly awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". Crick was an important theoretical molecular biologist and played a crucial role in research related to revealing the helical structure of DNA. He is widely known for use of the term "central dogma" to summarize the idea that genetic information flow in cells is essentially one-way, from DNA to RNA to protein. During the remainder of his career, he held the post of J.W. Kieckhefer Distinguished Research Professor at the Salk Institute for Biological Studies in La Jolla, California. His later research centered on theoretical neurobiology and attempts to advance the scientific study of human consciousness. He remained in this post until his death; "he was editing a manuscript on his death bed, a scientist until the bitter end" according to Christof Koch.

Matthias Jakob Schleiden (1804–1881)

Source: Wikipedia

Matthias Jakob Schleiden was a German botanist and co-founder of cell theory, along with Theodor Schwann and Rudolf Virchow. Born in Hamburg, Schleiden was educated at University of Jena, then practiced law in Heidelberg, but soon developed his love for botany into a full-time pursuit. Schleiden preferred to study plant structure under the microscope. While a professor of botany at the University of Jena, he wrote Contributions to our knowledge of phytogenesis (1838), in which he stated that all parts of the plant organism are composed of cells. Thus, Schleiden and Schwann became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, discovered in 1831 by the Scottish botanist Robert Brown, and sensed its connection with cell division. Schleiden was one of the first German biologists to accept Charles Darwin's theory of evolution. He became professor of botany at the University of Dorpat in 1863. He concluded that all plant parts are made of cells and that an embryonic plant organism arises from the one cell.

Theodor Schwann (1810–1882)

Source: Wikipedia

Theodor Schwann was a German physiologist. His many contributions to biology include the development of cell theory, the discovery of Schwann cells in the peripheral nervous system, the discovery and study of pepsin, the discovery of the organic nature of yeast, and the invention of the term metabolism. In 1837, Matthias Jakob Schleiden viewed and stated that new plant cells formed from the nuclei of old plant cells. While dining that year with Schwann, the conversation turned on the nuclei of plant and animal cells. Schwann remembered seeing similar structures in the cells of the notochord (as had been shown by Müller) and instantly realized the importance of connecting the two phenomena. The resemblance was confirmed without delay by both observers, and the results soon appeared in Schwann's famous Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants, in which he declared that "All living things are composed of cells and cell products". This became cell theory or cell doctrine. In the course of his verification of cell theory, Schwann proved the cellular origin and development of the most highly differentiated tissues including nails, feathers, and tooth enamel. Schwann established a basic principle of embryology by observing that the ovum is a single cell that eventually develops into a complete organism.

Rudolf Virchow (1821–1902)

Source: Wikipedia

Rudolf Ludwig Carl Virchow was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician, known for his advancement of public health. He is known as "the father of modern pathology" because his work helped to discredit humourism, bringing more science to medicine. He is also known as the founder of social medicine and veterinary pathology, and to his colleagues, the "Pope of medicine". A prolific writer, his scientific writings alone exceeded 2,000 in number. Among his books, Cellular Pathology published in 1858 is regarded as the root of modern pathology. This work also popularised the third dictum in cell theory: Omnis cellula e cellula ("All cells come from cells"); although his idea originated in 1855. Virchow is credited with several very important discoveries. His most widely known scientific contribution is his cell theory, which built on the work of Theodor Schwann. He was one of the first to accept the work of Robert Remak, who showed the origins of cells was the division of pre-existing cells. He did not initially accept the evidence for cell division, believing it only occurs in certain types of cells. When it dawned on him that Remak might be right, in 1855, he published Remak's work as his own, which caused a falling out between the two. This work, Virchow encapsulated in the epigram Omnis cellula e cellula ("all cells (come) from cells"), which he published in 1855. He was an ardent anti-evolutionist. He referred to Charles Darwin as an "ignoramus" and his own student Ernst Haeckel, the leading advocate of Darwinism in Germany, as a "fool". He discredited the original specimen of Neanderthal man as nothing but that of a deformed human, and not an ancestral species.

Hans Driesch (1867–1941)

Source: Wikipedia

Hans Adolf Eduard Driesch was a German biologist and philosopher from Bad Kreuznach. He is most noted for his early experimental work in embryology and for his neo-vitalist philosophy of entelechy. He is also credited with performing the first 'cloning' of an animal in the 1880s. Driesch was educated at the Gelehrtenschule des Johanneums. He began to study medicine in 1886 under August Weismann at the University of Freiburg. In 1887 he attended the University of Jena under Ernst Haeckel, Oscar Hertwig and Christian Ernst Stahl. In 1888 he studied physics and chemistry at the University of Munich. He received his doctorate in 1889. He travelled widely on field and study trips and lecture-tours, visiting Plymouth, India, Zurich and Leipzig where, in 1894, he published his Analytische Theorie der organischen Entwicklung or Analytic Theory of Organic Development. By 1885 Driesch's experiments on the sea urchin embryo suggested that it was possible to remove large pieces from eggs, shuffle the blastomeres and interfere in many ways without affecting the resulting embryo. It appeared that any single monad in the original egg cell was capable of forming any part of the completed embryo. This important refutation of both preformation and the mosaic theory of Wilhelm Roux was to be subject to much discussion in the ensuing years, and caused friction among Driesch, Roux and Haeckel. In his work on sea urchins, dividing cells of the embryo after the first cell-division, he expected each cell to develop into the corresponding half of the animal to which it has been destined or preprogrammed, but instead found that each developed into a complete sea urchin. This also happened at the four-cell stage: entire larvae ensued from each of the four cells, albeit smaller than usual. Driesch's findings brought about the adoption of the terms "totipotent" and "pluripotent" cell, referring respectively to a cell that can generate every cell in an organism and one that can generate nearly every cell. Driesch's results were confirmed with greater precision by Hans Spemann.

Oscar Hertwig (1849–1922)

Source: Wikipedia

Oscar Hertwig was a German zoologist and professor, who also wrote about the theory of evolution circa 1916, over 55 years after Charles Darwin's book The Origin of Species. Oscar Hertwig was a leader in the field of comparative and causal animal-developmental history. He also wrote a leading textbook. By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell. He recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he published his findings that fertilization includes the penetration of a spermatozoon into an egg cell. Oscar Hertwig experiments with frog eggs revealed the 'long axis rule', or Hertwig rule. According to this rule cell divides along its long axis (1884). While Oscar was well interested in developmental biology, he was opposed to chance as assumed in Charles Darwin´s theory. His most important theoretical book was: Das Werden der Organismen, eine Widerlegung der Darwinschen Zufallslehre (Jena, 1916) (translation: The Origin of Organisms – a Refutation of Darwin's Theory of Chance).

See Also:

Brind'Amour, Katherine,, Garcia, Benjamin, "Wilhelm August Oscar Hertwig (1849-1922)". Embryo Project Encyclopedia (2007-11-01). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1707.

Churchill, F B (1970), "Hertwig, Weismann, and the meaning of reduction division circa 1890.", Isis; an international review devoted to the history of science and its cultural influences, 61:429–57.

Edmund Beecher Wilson (1856–1939)

Source: Wikipedia

Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell in Development and Inheritance. He and Nettie Maria Stevens were the first researchers to describe the chromosomal basis of sex, but they conducted their research independently of each other. Wilson is credited as America's first cell biologist. In 1898 he used the similarity in embryos to describe phylogenetic relationships. By observing spiral cleavage in molluscs, flatworms and annelids he concluded that the same organs came from the same group of cells and concluded that all these organisms must have a common ancestor.

Theodor Boveri (1862–1915)

Source: Embryo Project

Theodor Heinrich Boveri was a German biologist. He was notable for first hypothesising the cellular processes that cause cancer. Boveri's work with sea urchins showed that it was necessary to have all chromosomes present in order for proper embryonic development to take place. This discovery was an important part of the Boveri–Sutton chromosome theory, which identifies chromosomes as the carriers of genetic material. The theory correctly explains the mechanism underlying the laws of Mendelian inheritance by identifying chromosomes with the paired factors (particles) required by Mendel's laws. The chromosome theory of inheritance is credited to papers by Walter Sutton in 1902 and 1903, as well as to independent work by Theodor Boveri during roughly the same period. Boveri's thoughts are summarized in his book Ergebnisse über die Konstitution der chromatischen Substanz des Zellkerns (Results on the constitution of the chromatic substance of the cell nucleus), Jena: Verlag von Gustav Fischer, 1904. His other significant discovery was the centrosome (1888), which he described as the especial organ of cell division. Boveri also discovered the phenomenon of chromatin diminution during embryonic development of the nematode Parascaris.

Thomas Hunt Morgan (1866–1945)

Source: Wikipedia

Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Morgan received his Ph.D. from Johns Hopkins University in zoology in 1890 and researched embryology during his tenure at Bryn Mawr. Following the rediscovery of Mendelian inheritance in 1900, Morgan began to study the genetic characteristics of the fruit fly Drosophila melanogaster. In his famous Fly Room at Columbia University, Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of genetics. During his distinguished career, Morgan wrote 22 books and 370 scientific papers. As a result of his work, Drosophila became a major model organism in contemporary genetics. The Division of Biology which he established at the California Institute of Technology has produced seven Nobel Prize winners.

See Also:

Garland E. Allen. 1979. Thomas Hunt Morgan: The Man and His Science. Princeton: Princeton University Press. 447 pp. (The definitive biography)

Robert E. Kohler. 1994. Lords of the Fly: Drosophila Genetics and the Experimental Life. Chicago: University of Chicago Press. 344pp. (An excellent treatment of the early work in Drosophila genetics)

H. J. Muller. 1946. Thomas Hunt Morgan 1866–1945. Science, 103:550–551.

Diana E. Kenney and Gary G. Borisy. 2009. Thomas Hunt Morgan at the Marine Biological Laboratory: Naturalist and Experimentalist. Genetics, 181:841-846.

R. A. Fisher and G. R. de Beer. 1947. Thomas Hunt Morgan. 1866–1945. Obituary Notices of Fellows of the Royal Society, 5:451-466.

Stephen G. Brush. 2002. How Theories became Knowledge: Morgan's Chromosome Theory of Heredity in America and Britain. Journal of the History of Biology, 35:471–535.

Norman H. Horowitz. 1998. T. H. Morgan at Caltech: A Reminiscence. Genetics, 149:1629–1632.

Hans Spemann (1869–1941)

Source: Wikipedia

Hans Spemann was a German embryologist who was awarded a Nobel Prize in Physiology or Medicine in 1935 for his discovery of the effect now known as embryonic induction, an influence, exercised by various parts of the embryo, that directs the development of groups of cells into particular tissues and organs. In 1893–1894 he moved to the University of Munich for clinical training but decided, rather than becoming a clinician, to move to the Zoological Institute at the University of Würzburg, where he remained as a lecturer until 1908. His degree in zoology, botany, and physics, awarded in 1895, followed study under Theodor Boveri, Julius Sachs and Wilhelm Röntgen. During the winter of 1896, while quarantined in a sanitarium recovering from tuberculosis, Spemann read August Weismann's book The Germ Plasm: A Theory of Heredity. He wrote in his autobiography: "I found here a theory of heredity and development elaborated with uncommon perspicacity to its ultimate consequences.....This stimulated experimental work of my own".

Spemann was appointed Professor of Zoology and Comparative Anatomy at Rostock in 1908 and, in 1914, Associate Director of the Kaiser Wilhelm Institute of Biology at Dahlem, Berlin. Here he undertook the experiments that would make him famous. Drawing upon the recent work of Warren H. Lewis[2] and Ethel Browne Harvey, he turned his skills to the gastrula, grafting a "field" of cells (the Primitive knot) from one embryo onto another. The experiments, aided by Hilde Pröscholdt (later Mangold), a Ph.D. candidate in Spemann's laboratory in Freiburg, took place over several years and were published in full only in 1924. They described an area in the embryo, the portions of which, upon transplantation into a second embryo, organized or "induced" secondary embryonic primordia regardless of location. Spemann called these areas "organiser centres" or "organisers". Later he showed that different parts of the organiser centre produce different parts of the embryo.

See Also:

Wellner, Karen, "Hans Spemann (1869-1941)". Embryo Project Encyclopedia (2010-06-15). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1688.

The Nobel Prize in Physiology or Medicine 1935: Hans Spemann

Hans Spemann. 1935. Nobel Lecture: The Organizer-Effect in Embryonic Development

Richard Goldschmidt (1878–1958)

Source: Wikipedia

Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony. Controversially, Goldschmidt advanced a model of macroevolution through macromutations that is popularly known as the "Hopeful Monster" hypothesis. Goldschmidt also described the nervous system of the nematode, a piece of work that later influenced Sydney Brenner to study the wiring diagram of Caenorhabditis elegans an achievement that later won Brenner and his colleagues the Nobel Prize in 2002.

In 1903 Goldschmidt began working as an assistant to Richard Hertwig at the University of Munich, where he continued his work on nematodes and their histology, including studies of the nervous system development of Ascaris and the anatomy of Amphioxus. He founded the histology journal Archiv für Zellforschung while working in Hertwig's laboratory. Under Hertwig's influence, he also began to take an interest in chromosome behavior and the new field of genetics. In 1909 Goldschmidt became professor at the University of Munich and, inspired by Wilhelm Johannsen's genetics treatise Elemente der exakten Erblichkeitslehre, began to study sex determination and other aspects of the genetics of the gypsy moth. His studies of the gypsy moth, which culminated in his 1934 monograph Lymantria, became the basis for his theory of sex determination, which he developed from 1911 until 1931. Goldschmidt left Munich in 1914 for the position as head of the genetics section of the newly founded Kaiser Wilhelm Institute for Biology. During a field trip to Japan in 1914 he was not able to return to Germany due to the outbreak of the First World War and got stranded in the United States. He ended up in an internment camp in Fort Oglethorpe, Georgia for "dangerous Germans". After his release in 1918 he returned to Germany in 1919 and worked at the Kaiser Wilhelm Institute. Sensing that it was unsafe for him to remain in Germany he emigrated to the United States 1936, where he became professor at the University of California, Berkeley. During World War 2, the Nazi party published a propaganda poster entitled "Jewish World Domination" displaying the Goldschmidt family tree.

Goldschmidt was the first scientist to use the term "hopeful monster". He thought that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution. In his book The Material Basis of Evolution (1940), he wrote "the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation." Goldschmidt believed the large changes in evolution were caused by macromutations (large mutations). His ideas about macromutations became known as the hopeful monster hypothesis, which is considered a type of saltational evolution. According to Goldschmidt, biologists seem inclined to think that because they have not themselves seen a 'large' mutation, such a thing cannot be possible. But such a mutation need only be an event of the most extraordinary rarity to provide the world with the important material for evolution. The origin of the first eukaryotic cell might be considered an example of a Goldschmidtian hopeful monster.

See Also:

Dietrich, Michael R. 2003. Richard Goldschmidt: hopeful monsters and other 'heresies'. Nature reviews Genetics, 4:68-74.

Thomas Robert Malthus (1766–1834)

Source: Wikipedia

Thomas Robert Malthus was an English cleric and scholar, influential in the fields of political economy and demography. Malthus himself used only his middle name, Robert. In his book An Essay on the Principle of Population, Malthus observed that an increase in a nation's food production improved the well-being of the populace, but the improvement was temporary because it led to population growth, which in turn restored the original per capita production level. In other words, mankind had a propensity to utilize abundance for population growth rather than for maintaining a high standard of living, a view that has become known as the "Malthusian trap" or the "Malthusian spectre". Populations had a tendency to grow until the lower class suffered hardship and want and greater susceptibility to famine and disease, a view that is sometimes referred to as a Malthusian catastrophe. Malthus wrote in opposition to the popular view in 18th-century Europe that saw society as improving and in principle as perfectible. He saw population growth as being inevitable whenever conditions improved, thereby precluding real progress towards a utopian society: "The power of population is indefinitely greater than the power in the earth to produce subsistence for man". His views became influential, and controversial, across economic, political, social and scientific thought. Pioneers of evolutionary biology read him, notably Charles Darwin and Alfred Russel Wallace.

Jean-Baptiste Lamarck (1744–1829)

Source: Wikipedia

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, often known simply as Lamarck, was a French naturalist. He was a soldier, biologist, academic, and an early proponent of the idea that biological evolution occurred and proceeded in accordance with natural laws. In 1801, he published Système des animaux sans vertèbres, a major work on the classification of invertebrates, a term he coined. In an 1802 publication he became one of the first to use the term biology in its modern sense. Lamarck continued his work as a premier authority on invertebrate zoology. He is remembered, at least in malacology, as a taxonomist of considerable stature. The modern era generally remembers Lamarck for a theory of inheritance of acquired characteristics, called soft inheritance, Lamarckism or use/disuse theory, which he described in his 1809 Philosophie Zoologique. However, his idea of soft inheritance was, perhaps, a reflection of the wisdom of the time accepted by many natural historians. Lamarck's contribution to evolutionary theory consisted of the first truly cohesive theory of biological evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through use and disuse of characteristics, differentiating them from other organisms. Scientists have debated whether advances in the field of transgenerational epigenetics mean that Lamarck was to an extent correct, or not.

Charles Darwin (1809–1882)

Source: Wikipedia

Charles Robert Darwin was an English naturalist, geologist and biologist, best known for his contributions to the science of evolution. He established that all species of life have descended over time from common ancestors and, in a joint publication with Alfred Russel Wallace, introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. Darwin published his theory of evolution with compelling evidence in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species. By the 1870s, the scientific community and much of the general public had accepted evolution as a fact. However, many favoured competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed in which natural selection was the basic mechanism of evolution. In modified form, Darwin's scientific discovery is the unifying theory of the life sciences, explaining the diversity of life.

See Also:

Darwin Online: The world's largest and most widely used resource on Darwin, containing his complete publications, his private papers and manuscripts, and much supplementary material.

Alfred Russel Wallace (1823–1913)

Source: Wikipedia

Alfred Russel Wallace was a British naturalist, explorer, geographer, anthropologist, and biologist. He is best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858. This prompted Darwin to publish his own ideas in On the Origin of Species. Wallace did extensive fieldwork, first in the Amazon River basin and then in the Malay Archipelago, where he identified the faunal divide now termed the Wallace Line, which separates the Indonesian archipelago into two distinct parts: a western portion in which the animals are largely of Asian origin, and an eastern portion where the fauna reflect Australasia. He was considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography". Wallace was one of the leading evolutionary thinkers of the 19th century and made many other contributions to the development of evolutionary theory besides being co-discoverer of natural selection. These included the concept of warning colouration in animals, and the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridisation. Wallace was strongly attracted to unconventional ideas (such as evolution). His advocacy of spiritualism and his belief in a non-material origin for the higher mental faculties of humans strained his relationship with some members of the scientific establishment.

See Also:

The Alfred Russel Wallace Website

Encyclopædia Britannica: Alfred Russel Wallace

The Alfred Russel Wallace Page

The New Yorker: Missing Link, Alfred Russel Wallace, Charles Darwin’s neglected double.

NOVA: Great Minds Think Alike, How Alfred Wallace Came to Share Darwin's Revolutionary Insight

Wallace Online (the first complete edition of the writings of Alfred Russel Wallace, including the first compilation of his specimens)

Alfred Russel Wallace, Darwin Correspondence Project

Thomas Huxley (1825–1895)

Source: Wikipedia

Thomas Henry Huxleywas an English biologist specialising in comparative anatomy. He is known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution. Huxley's famous debate in 1860 with Samuel Wilberforce was a key moment in the wider acceptance of evolution and in his own career. Huxley had been planning to leave Oxford on the previous day, but, after an encounter with Robert Chambers, the author of Vestiges, he changed his mind and decided to join the debate. Wilberforce was coached by Richard Owen, against whom Huxley also debated about whether humans were closely related to apes.

Huxley was slow to accept some of Darwin's ideas, such as gradualism, and was undecided about natural selection, but despite this he was wholehearted in his public support of Darwin. Instrumental in developing scientific education in Britain, he fought against the more extreme versions of religious tradition. Huxley was certainly not slavish in his dealings with Darwin. As shown in every biography, they had quite different and rather complementary characters. Important also, Darwin was a field naturalist, but Huxley was an anatomist, so there was a difference in their experience of nature. Lastly, Darwin's views on science were different from Huxley's views. For Darwin, natural selection was the best way to explain evolution because it explained a huge range of natural history facts and observations: it solved problems. Huxley, on the other hand, was an empiricist who trusted what he could see, and some things are not easily seen. With this in mind, one can appreciate the debate between them, Darwin writing his letters, Huxley never going quite so far as to say he thought Darwin was right.

Huxley's reservations on natural selection were of the type "until selection and breeding can be seen to give rise to varieties which are infertile with each other, natural selection cannot be proved". Huxley's position on selection was agnostic; yet he gave no credence to any other theory. Huxley was for about thirty years evolution's most effective advocate, and for some Huxley was "the premier advocate of science in the nineteenth century [for] the whole English-speaking world". [Lyons, Sherrie L (1999), Thomas Henry Huxley: the evolution of a scientist, New York.]

Ernst Haeckel (1834–1919)

Source: Wikipedia

Ernst Heinrich Philipp August Haeckel was a German biologist, naturalist, philosopher, physician, professor, marine biologist, and artist who discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms, and coined many terms in biology, including anthropogeny, ecology, phylum, phylogeny, stem cell, and Protista. Haeckel promoted and popularised Charles Darwin's work in Germany and developed the influential but no longer widely held recapitulation theory (ontogeny recapitulates phylogeny) claiming that an individual organism's biological development, or ontogeny, parallels and summarises its species' evolutionary development, or phylogeny. Haeckel studied under Karl Gegenbaur at the University of Jena for three years, earning a doctorate in zoology, before becoming a professor of comparative anatomy at the University of Jena, where he remained for 47 years, from 1862 to 1909. Between 1859 and 1866, Haeckel worked on many phyla such radiolarians, poriferans (sponges) and annelids (segmented worms). During a trip to the Mediterranean, Haeckel named nearly 150 new species of radiolarians. Haeckel was a zoologist, an accomplished artist and illustrator, and later a professor of comparative anatomy. He was one of the first to consider psychology as a branch of physiology. He also proposed the kingdom Protista in 1866. His chief interests lay in evolution and life development processes in general, including development of nonrandom form, which culminated in the beautifully illustrated Kunstformen der Natur (Art forms of nature). Darwin's 1859 book On the Origin of Species had immense popular influence, but although its sales exceeded its publisher's hopes it was a technical book rather than a work of popular science: long, difficult and with few illustrations. One of Haeckel's books did a great deal to explain his version of "Darwinism" to the world. It was a bestselling, provocatively illustrated book in German, titled Natürliche Schöpfungsgeschichte, published in Berlin in 1868, and translated into English as The History of Creation in 1876. It was frequently reprinted until 1926.

See Also:

The Tragic Sense of Life: Ernst Haeckel and the Struggle over Evolutionary Thought — an excellent biography of Haeckel.

William Keith Brooks (1848–1908)

Source: Wikipedia

William Keith Brooks received a Bachelor of Arts degree from Williams College in 1870 and a PhD from Harvard in 1875. With the opening of The Johns Hopkins University in 1876, Brooks received one of the university's initial fellowships and he quickly advanced within the organization, ultimately serving as Professor of Zoology and Head of the Biological Department. At the young age of 36 he was elected a member of the National Academy. He was chosen as a member of the American Philosophical Society in 1886 and of the Academy of Natural Science in 1887. Although many of Brooks' scientific contributions represent solid, nineteeth-century work, his most lasting effect came from his long-standing conviction that the processes of heredity were themselves a proper subject of investigation. In 1876 he wrote a paper entitled "A Provisional Hypothesis of Pangenesis" and he gave the subject a book-length treatment in his The Law of Heredity. A Study of the Cause of Variation and the Origin of Living Organisms. He was known as both a man of deep, abstract thought and an excellent teacher, as evidenced by the fact that many of the still well-known pioneers of genetics had, at one time or another, studied with him: viz. Thomas Morgan, E. B. Wilson, and William Bateson.

Oscar Hertwig (1849–1922)

Source: Wikipedia

Oscar Hertwig was a German zoologist and professor, who also wrote about the theory of evolution circa 1916, over 55 years after Charles Darwin's book The Origin of Species. Oscar Hertwig was a leader in the field of comparative and causal animal-developmental history. He also wrote a leading textbook. By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell. He recognized the role of the cell nucleus during inheritance and chromosome reduction during meiosis: in 1876, he published his findings that fertilization includes the penetration of a spermatozoon into an egg cell. Oscar Hertwig experiments with frog eggs revealed the 'long axis rule', or Hertwig rule. According to this rule cell divides along its long axis (1884). While Oscar was well interested in developmental biology, he was opposed to chance as assumed in Charles Darwin´s theory. His most important theoretical book was: Das Werden der Organismen, eine Widerlegung der Darwinschen Zufallslehre (Jena, 1916) (translation: The Origin of Organisms – a Refutation of Darwin's Theory of Chance).

See Also:

Brind'Amour, Katherine,, Garcia, Benjamin, "Wilhelm August Oscar Hertwig (1849-1922)". Embryo Project Encyclopedia (2007-11-01). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/1707.

Churchill, F B (1970), "Hertwig, Weismann, and the meaning of reduction division circa 1890.", Isis; an international review devoted to the history of science and its cultural influences, 61:429–57.

August Weismann (1834–1914)

Source: Wikipedia

August Friedrich Leopold Weismann was a German evolutionary biologist. Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg. His main contribution involved his Germ Plasm Theory, at one time also known as Weismannism, according to which inheritance (in a multicellular organism) only takes place by means of the germ cells — the gametes such as egg cells and sperm cells. Other cells of the body — somatic cells — do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. The idea of the Weismann barrier is central to the modern evolutionary synthesis, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection. Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time".

See Also:

Essays Upon Heredity — a collection of Weismann's writing on hereditary issues.

Yawen Zou. 2015. The Germ-Plasm: a Theory of Heredity (1893), by August Weismann. The Embryo Project Encyclopedia.

Edwin G. Conklin. 1915. August Weismann. Proceedings of the American Philosophical Society, 54:3-12.

Hugo de Vries (1848–1935)

Source: Wikipedia

Hugo Marie de Vries was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution. In 1889, De Vries published his book Intracellular Pangenesis, in which, based on a modified version of Charles Darwin's theory of Pangenesis of 1868, he postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles. He called these units pangenes, a term 20 years later to be shortened to genes by Wilhelm Johannsen.

See Also:

Ralph E. Cleland. 1936. Hugo de Vries. Proceedings of the American Philosophical Society, 76:248-250.

Thomas Hunt Morgan (1866–1945)

Source: Wikipedia

Thomas Hunt Morgan was an American evolutionary biologist, geneticist, embryologist, and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Morgan received his Ph.D. from Johns Hopkins University in zoology in 1890 and researched embryology during his tenure at Bryn Mawr. Following the rediscovery of Mendelian inheritance in 1900, Morgan began to study the genetic characteristics of the fruit fly Drosophila melanogaster. In his famous Fly Room at Columbia University, Morgan demonstrated that genes are carried on chromosomes and are the mechanical basis of heredity. These discoveries formed the basis of the modern science of genetics. During his distinguished career, Morgan wrote 22 books and 370 scientific papers. As a result of his work, Drosophila became a major model organism in contemporary genetics. The Division of Biology which he established at the California Institute of Technology has produced seven Nobel Prize winners.

See Also:

Garland E. Allen. 1979. Thomas Hunt Morgan: The Man and His Science. Princeton: Princeton University Press. 447 pp. (The definitive biography)

Robert E. Kohler. 1994. Lords of the Fly: Drosophila Genetics and the Experimental Life. Chicago: University of Chicago Press. 344pp. (An excellent treatment of the early work in Drosophila genetics)

H. J. Muller. 1946. Thomas Hunt Morgan 1866–1945. Science, 103:550–551.

Diana E. Kenney and Gary G. Borisy. 2009. Thomas Hunt Morgan at the Marine Biological Laboratory: Naturalist and Experimentalist. Genetics, 181:841-846.

R. A. Fisher and G. R. de Beer. 1947. Thomas Hunt Morgan. 1866–1945. Obituary Notices of Fellows of the Royal Society, 5:451-466.

Stephen G. Brush. 2002. How Theories became Knowledge: Morgan's Chromosome Theory of Heredity in America and Britain. Journal of the History of Biology, 35:471–535.

Norman H. Horowitz. 1998. T. H. Morgan at Caltech: A Reminiscence. Genetics, 149:1629–1632.

Richard Goldschmidt (1878–1958)

Source: Wikipedia

Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony. Controversially, Goldschmidt advanced a model of macroevolution through macromutations that is popularly known as the "Hopeful Monster" hypothesis. Goldschmidt also described the nervous system of the nematode, a piece of work that later influenced Sydney Brenner to study the wiring diagram of Caenorhabditis elegans an achievement that later won Brenner and his colleagues the Nobel Prize in 2002.

In 1903 Goldschmidt began working as an assistant to Richard Hertwig at the University of Munich, where he continued his work on nematodes and their histology, including studies of the nervous system development of Ascaris and the anatomy of Amphioxus. He founded the histology journal Archiv für Zellforschung while working in Hertwig's laboratory. Under Hertwig's influence, he also began to take an interest in chromosome behavior and the new field of genetics. In 1909 Goldschmidt became professor at the University of Munich and, inspired by Wilhelm Johannsen's genetics treatise Elemente der exakten Erblichkeitslehre, began to study sex determination and other aspects of the genetics of the gypsy moth. His studies of the gypsy moth, which culminated in his 1934 monograph Lymantria, became the basis for his theory of sex determination, which he developed from 1911 until 1931. Goldschmidt left Munich in 1914 for the position as head of the genetics section of the newly founded Kaiser Wilhelm Institute for Biology. During a field trip to Japan in 1914 he was not able to return to Germany due to the outbreak of the First World War and got stranded in the United States. He ended up in an internment camp in Fort Oglethorpe, Georgia for "dangerous Germans". After his release in 1918 he returned to Germany in 1919 and worked at the Kaiser Wilhelm Institute. Sensing that it was unsafe for him to remain in Germany he emigrated to the United States 1936, where he became professor at the University of California, Berkeley. During World War 2, the Nazi party published a propaganda poster entitled "Jewish World Domination" displaying the Goldschmidt family tree.

Goldschmidt was the first scientist to use the term "hopeful monster". He thought that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution. In his book The Material Basis of Evolution (1940), he wrote "the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation." Goldschmidt believed the large changes in evolution were caused by macromutations (large mutations). His ideas about macromutations became known as the hopeful monster hypothesis, which is considered a type of saltational evolution. According to Goldschmidt, biologists seem inclined to think that because they have not themselves seen a 'large' mutation, such a thing cannot be possible. But such a mutation need only be an event of the most extraordinary rarity to provide the world with the important material for evolution. The origin of the first eukaryotic cell might be considered an example of a Goldschmidtian hopeful monster.

See Also:

Dietrich, Michael R. 2003. Richard Goldschmidt: hopeful monsters and other 'heresies'. Nature reviews Genetics, 4:68-74.

Theodosius Dobzhansky (1900–1975)

Source: Wikipedia

Theodosius Grygorovych Dobzhanskywas a prominent Russian-American geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the unifying modern evolutionary synthesis. Dobzhansky was born in Ukraine, then part of the Russian Empire, and became an immigrant to the United States in 1927, aged 27 years old. His 1937 work Genetics and the Origin of Species became a major influence on the synthesis and was awarded the US National Medal of Science in 1964, and the Franklin Medal in 1973.

Dobzhansky immigrated to the United States in 1927 on a scholarship from the International Education Board of the Rockefeller Foundation to work and study in the United States. Arriving in New York City on December 27, he worked with Thomas Hunt Morgan at Columbia University, who had pioneered the use of fruit flies (Drosophila melanogaster) in genetics experiments. He followed Morgan to the California Institute of Technology from 1930 to 1940. On the basis of his experiments, he articulated the idea that reproductive isolation can be caused by differences in presence of microbial symbionts between populations. In 1937, he published one of the major works of the modern evolutionary synthesis, the synthesis of evolutionary biology with genetics, entitled Genetics and the Origin of Species, which amongst other things, defined evolution as "a change in the frequency of an allele within a gene pool". Dobzhansky's work was instrumental in spreading the idea that it is through mutations in genes that natural selection takes place. Also in 1937, he became a naturalized citizen of the United States. During this time, he had a very public falling out with one of his Drosophila collaborators, Alfred Sturtevant, based primarily in professional competition.

Dobzhansky's wife Natasha died of coronary thrombosis on February 22, 1969. Earlier (on June 1, 1968) Theodosius had been diagnosed with lymphocytic leukemia (a chronic form of leukemia), and had been given a few months to a few years to live. He retired in 1971, moving to the University of California, Davis where his student Francisco Jose Ayala had been made assistant professor, and where he continued working as an emeritus professor. He published one of his most famous essays "Nothing in Biology Makes Sense Except in the Light of Evolution" at this time, influenced by the paleontologist/priest Pierre Teilhard de Chardin. By 1975, his leukemia had become more severe, and on November 11 he traveled to San Jacinto, California for treatment and care. He died (of heart failure) on December 18.

See Also:

Theodosius Dobzhansky. 1973. Nothing in Biology Makes Sense except in the Light of Evolution. The American Biology Teacher, 35:125-129.

Collected papers from a NAS colloquium on Dobzhansky's Genetics and the Origin of Species

Francisco J. Ayala. 1985. Theodosius Dobzhansky 1900 – 1975. Biographical Memoirs, National Academy of Sciences.

Theodosius Dobzhansky Papers. Americal Philosophical Society

Julian Huxley (1887–1975)

Source: Wikipedia

Sir Julian Sorell Huxley was a British evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern evolutionary synthesis. He was secretary of the Zoological Society of London (1935–1942), the first Director of UNESCO, a founding member of the World Wildlife Fund and the first President of the British Humanist Association. Huxley came from the distinguished Huxley family. His brother was the writer Aldous Huxley, and his half-brother a fellow biologist and Nobel laureate, Andrew Huxley; his father was writer and editor Leonard Huxley; and his paternal grandfather was Thomas Henry Huxley, a friend and supporter of Charles Darwin and proponent of evolution. His maternal grandfather was the academic Tom Arnold, his great-uncle was poet Matthew Arnold and his great-grandfather was Thomas Arnold of Rugby School.

Huxley was one of the main architects of the modern evolutionary synthesis which took place around the time of World War II. The synthesis of genetic and population ideas produced a consensus which reigned in biology from about 1940, and which is still broadly tenable. His book Evolution: The Modern Synthesis was written while he was secretary to the Zoological Society, and made use of his remarkable collection of reprints covering the first part of the century. It was published in 1942. Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing". Huxley's main co-respondents in the modern evolutionary synthesis are usually listed as Ernst Mayr, Theodosius Dobzhansky, George Gaylord Simpson, Bernhard Rensch, Ledyard Stebbins and the population geneticists J. B. S. Haldane, Ronald Fisher and Sewall Wright.

Despite its ecstatic initial reception, the limits of Huxley's Modern Synthesis are now becoming more obvious. A particular problem is the book's completely inadequate treatment of microbial genetics:

Bacteria ... appear to be not only wholly asexual but premitotic. Their hereditary constitution is not differentiated into specialized parts with different functions. They have no genes in the sense of accurately quantized portions of hereditary substance; and therefore they have no need for the accurate division of the genetic system which is accomplished by mitosis. ... That occasional 'mutations' occur we know, but there is no ground for supposing that they are similar in nature to those of higher organisms, nor, since they are usually reversible according to conditions, that they play the same part in evolution. We must, in fact, expect that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms. J. Huxley, 1943, Evolution: The Modern Synthesis, New York: Harper & Brothers Publishers, pp. 131–132.

Although it is now clear that the processes of variation, heredity, and evolution in bacteria are quite different from the corresponding processes in multicellular organisms, this is not because bacteria possess no genes in the sense of accurately quantized portions of hereditary substance.

Carl Woese (1928–2012)

Source: Wikipedia

Carl Richard Woese was an American microbiologist and biophysicist. Woese is famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese which revolutionized the discipline of microbiology. He was also the originator of the RNA world hypothesis in 1967, although not by that name. He held the Stanley O. Ikenberry Chair and was professor of microbiology at the University of Illinois at Urbana–Champaign. For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their biochemistry, morphology and metabolism. In a highly influential 1962 paper, Roger Stanier and C. B. van Niel first established the division of cellular organization into prokaryotes and eukaryotes, defining prokaryotes as those organisms lacking a cell nucleus. Stanier and Van Niel's concept was quickly accepted as the most important distinction among organisms; yet they were nevertheless skeptical of microbiologists' attempts to construct a natural phylogenetic classification of bacteria. However, it became generally assumed that all life shared a common prokaryotic (implied by the Greek root pro- (before, in front of) ancestor. In 1977, Carl Woese and George E. Fox experimentally disproved this universally held hypothesis about the basic structure of the tree of life. Woese and Fox discovered a kind of microbial life which they called the “archaebacteria” (Archaea). They reported that the archaebacteria comprised "a third kingdom" of life as distinct from bacteria as plants and animals. Having defined Archaea as a new "urkingdom" (later domain) which were neither bacteria nor eukaryotes, Woese redrew the taxonomic tree. His three-domain system, based on phylogenetic relationships rather than obvious morphological similarities, divided life into 23 main divisions, incorporated within three domains: Bacteria, Archaea, and Eucarya.

See Also:

Looking in the Right Direction: Carl Woese and the New Biology

Ernst Haeckel (1834–1919)

Source: Wikipedia

Ernst Heinrich Philipp August Haeckel was a German biologist, naturalist, philosopher, physician, professor, marine biologist, and artist who discovered, described and named thousands of new species, mapped a genealogical tree relating all life forms, and coined many terms in biology, including anthropogeny, ecology, phylum, phylogeny, stem cell, and Protista. Haeckel promoted and popularised Charles Darwin's work in Germany and developed the influential but no longer widely held recapitulation theory (ontogeny recapitulates phylogeny) claiming that an individual organism's biological development, or ontogeny, parallels and summarises its species' evolutionary development, or phylogeny. Haeckel studied under Karl Gegenbaur at the University of Jena for three years, earning a doctorate in zoology, before becoming a professor of comparative anatomy at the University of Jena, where he remained for 47 years, from 1862 to 1909. Between 1859 and 1866, Haeckel worked on many phyla such radiolarians, poriferans (sponges) and annelids (segmented worms). During a trip to the Mediterranean, Haeckel named nearly 150 new species of radiolarians. Haeckel was a zoologist, an accomplished artist and illustrator, and later a professor of comparative anatomy. He was one of the first to consider psychology as a branch of physiology. He also proposed the kingdom Protista in 1866. His chief interests lay in evolution and life development processes in general, including development of nonrandom form, which culminated in the beautifully illustrated Kunstformen der Natur (Art forms of nature). Darwin's 1859 book On the Origin of Species had immense popular influence, but although its sales exceeded its publisher's hopes it was a technical book rather than a work of popular science: long, difficult and with few illustrations. One of Haeckel's books did a great deal to explain his version of "Darwinism" to the world. It was a bestselling, provocatively illustrated book in German, titled Natürliche Schöpfungsgeschichte, published in Berlin in 1868, and translated into English as The History of Creation in 1876. It was frequently reprinted until 1926.

See Also:

The Tragic Sense of Life: Ernst Haeckel and the Struggle over Evolutionary Thought — an excellent biography of Haeckel.

Carl Woese (1928–2012)

Source: Wikipedia

Carl Richard Woese was an American microbiologist and biophysicist. Woese is famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese which revolutionized the discipline of microbiology. He was also the originator of the RNA world hypothesis in 1967, although not by that name. He held the Stanley O. Ikenberry Chair and was professor of microbiology at the University of Illinois at Urbana–Champaign. For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their biochemistry, morphology and metabolism. In a highly influential 1962 paper, Roger Stanier and C. B. van Niel first established the division of cellular organization into prokaryotes and eukaryotes, defining prokaryotes as those organisms lacking a cell nucleus. Stanier and Van Niel's concept was quickly accepted as the most important distinction among organisms; yet they were nevertheless skeptical of microbiologists' attempts to construct a natural phylogenetic classification of bacteria. However, it became generally assumed that all life shared a common prokaryotic (implied by the Greek root pro- (before, in front of) ancestor. In 1977, Carl Woese and George E. Fox experimentally disproved this universally held hypothesis about the basic structure of the tree of life. Woese and Fox discovered a kind of microbial life which they called the “archaebacteria” (Archaea). They reported that the archaebacteria comprised "a third kingdom" of life as distinct from bacteria as plants and animals. Having defined Archaea as a new "urkingdom" (later domain) which were neither bacteria nor eukaryotes, Woese redrew the taxonomic tree. His three-domain system, based on phylogenetic relationships rather than obvious morphological similarities, divided life into 23 main divisions, incorporated within three domains: Bacteria, Archaea, and Eucarya.

See Also:

Looking in the Right Direction: Carl Woese and the New Biology