Barbara McClintock

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Barbara McClintock (1947)

Barbara McClintock (* as Eleanor McClintock June 16, 1902 in Hartford , Connecticut ; † September 2, 1992 in Huntington , New York ) was an American geneticist and botanist . In the 1930s and 1940s she was one of the leading cytogenetics . She received the Nobel Prize in 1983 for her most important discovery from today's perspective, the occurrence of transposons (“jumping genes”) in maize (1948) . Another important contribution was her involvement in clearing up the crossing-over as early as 1931 .

Childhood, adolescence and studies

Barbara McClintock was the third of four children of doctor Thomas Henry McClintock and pianist Sara Handy McClintock. Her original first name was Eleanor; however, she has been called Barbara since early childhood because that seemed to suit her parents better to her spirited and boyish nature. From 1908 the family lived in the New York borough of Brooklyn , where Barbara and her siblings spent their school days. Barbara was very inquisitive and read a lot, but was also enthusiastic about sports. In order to be able to play baseball and football with her brother and his friends , she was given pants, which was very unusual for girls at the time. In other ways, too, the parents supported the individual interests of their children and defended them against the need to adapt. If Barbara wanted to skate in suitable weather, for example , she was allowed to stay away from class.

Barbara McClintock (third from right) with her siblings and her mother (at the piano)

Barbara McClintock was unusually independent even as a child. She remained single throughout her life, and she stated that she had never felt the need to bond or even understood why one should get married. Her wish to study almost never came true, as her mother, worried that she would then hardly find a husband, was decidedly against it and her father was in Europe as a field doctor . After graduating from high school a year earlier than usual in 1918 , Barbara - only 16 years old - initially worked as a recruiter . However, after the father's return, the parents agreed to support her wish. She enrolled at Cornell University in Ithaca , New York , one of the two universities in the United States that were specifically open to female science students. She was enrolled in agriculture, but her interests were broad; she also attended courses in meteorology and political science . She also took an active part in student life, being particularly interested in the Jewish students, who were still marginalized at the time, and therefore learned Yiddish . For a while she played the banjo in a jazz band specializing in improvisation , although she had little previous knowledge .

Early research at Cornell

During her studies at Cornell, McClintock began investigating the new field of cytogenetics . She became the assistant to the botanist Lowell Randolph , with whom she first described a triploid corn plant . In 1926 she was involved in a scientific publication for the first time. It also solved a problem for Randolph on which he had been working unsuccessfully for several years: distinguishing between the 10 different chromosomes of corn. While Randolph looked at preparations in the metaphase of mitosis in the root tip, in which they are maximally condensed, as was customary up to then , McClintock chose the pachytene stage of meiotic prophase in pollen mother cells . In addition, she did not prepare slices , but took up a new technique: the squeeze preparation , in which the object is spread under a cover slip. In a short time she was able to distinguish all 10 chromosomes of the haploid set. Randolph was by no means happy about this situation, however, and McClintock switched to Lester W. Sharp as assistant , who let her research independently and also became her doctoral supervisor.

McClintock received her PhD in 1927. The subject of her dissertation was the triploid corn, which she had already researched with Randolph. The corn remained her research object throughout her life. In the next few years she worked mainly with the future Nobel Prize winner George Beadle and with Marcus M. Rhoades , who came to Cornell to do their doctorate and showed great interest in their work. During the economically difficult years of the Great Depression , the three young scientists lived largely on grants from the National Research Council .

Since it was now possible to differentiate the 10 chromosomes of the maize, it was the logical next step for McClintock to assign each of the coupling groups known from genetic studies ( genes inherited from crossings ) to a chromosome. For this purpose, she crossed normal diploid plants with those in which one chromosome was present in triplicate ( trisomy ) and looked for irregularities in the inheritance of known genes. In this way she was able to associate all 10 chromosomes with coupling groups - partly alone, partly with colleagues - until 1931.

In 1930, Harriet B. Creighton , a student, began studying corn crossing-over as part of her dissertation under McClintock's guidance . It has long been known that linkage groups are not immutable, but can be combined anew, and it was assumed that this happens when homologous chromosome segments are exchanged during meiosis, which could be observed microscopically. However, there was no proof of this connection. McClintock had designed experiments to prove it and gave Creighton suitable test plants. When Thomas Hunt Morgan came to Cornell the following year and heard of Creighton's first successes, he persuaded her and McClintock to publish their previous results immediately, because he knew that Curt Stern was carrying out corresponding studies with Drosophila flies in Berlin . The maize researchers actually wanted to collect more data on what would have lasted an entire vegetation period, while with Drosophila one generation only takes 10 days. Because of Morgan's intervention, Creighton's and McClintock's article appeared shortly before Stern's work.

Difficult years in different places

Until 1931 McClintock stayed at Cornell University, where she was able to research freely alongside a teaching position. Then she received a grant from the National Research Council, which enabled her to spend two years visiting other research institutions. The first stay was with Lewis Stadler , one of the discoverers of the mutagenic effects of X-rays (1927), at the University of Missouri in Columbia , Missouri . There she investigated the effects of X-rays on the structure of corn chromosomes: translocations , inversions , deletions and the formation of ring chromosomes . At the invitation of Thomas Hunt Morgan, she continued this research at the California Institute of Technology (Caltech) in Pasadena , California , where she elucidated the formation of the nucleolus , a conspicuous structure in the cell nucleus with a then unknown function, and the nucleolus organizer region as part of one Chromosome discovered.

In 1933, on recommendations from Morgan, Sharp, Stadler and others, McClintock received a grant from the Guggenheim Foundation to enable her to work with Curt Stern in Berlin. Shortly before, however, Adolf Hitler had come to power, and Jewish scholars like Stern faced initial repression. Stern moved to Caltech in California and never returned to Germany. The Guggenheim Foundation urged McClintock to go to the Kaiser Wilhelm Institute in Berlin as planned. There she found an interesting interlocutor in Richard Goldschmidt, director of the institute , although he rejected the concepts of the gene and mutation . The political situation, for which she was not prepared, shocked her so much that Goldschmidt suggested after a few weeks that she should leave Berlin and arranged a stay with Friedrich Oehlkers in Freiburg im Breisgau . However, she did not stay there long either, and the Guggenheim Foundation agreed to return to the United States early.

McClintock was doing research again at Cornell, and after the Guggenheim Fellowship ended, Morgan, supported by Stern, brokered two-year funding from the Rockefeller Foundation . However, she was dissatisfied and not very productive at this time; In 1936, for the first time, she did not have a single publication. Her friends Rhoades, Beadle, and Creighton had left Cornell and taken jobs elsewhere during this difficult time that did not match their qualifications. McClintock saw no perspective for himself. However, efforts were made at several universities to create a position for her.

In 1936, on the initiative of Lewis Stadler, she was appointed Assistant Professor at the University of Missouri, where she studied chromosome breaks in corn caused by X-rays. She described that the breakpoints can later reunite and that this leads to massive mutations. Their observation that fractures can “heal” under certain conditions led to the concept of the telomere . Despite being a faculty member for the first time, McClintock viewed her position in Columbia as a temporary measure. The position of assistant professor did not do justice to her reputation and skills, and no opportunities for advancement opened up. She also felt isolated in the staff, while she increasingly made herself unpopular by disregarding conventions and bluntly criticizing the achievements of others. Stadler was not spared, either, and she developed a suspicion against him for which her biographers could find no rational reasons. After a discussion with the dean of the faculty, she decided in 1941 to leave the university.

Cold Spring Harbor

McClintock turned to Marcus Rhoades, who had just started a position at Columbia University in New York , to see if he could find her a visiting professorship there. Rhoades was enthusiastic and began to initiate this. In the same year, Milislav Demerec offered her a one-year position immediately after he took up the position of director of the genetics department at the Carnegie Institution in Cold Spring Harbor . After some hesitation, McClintock decided on the latter offer, in which she did not undertake any duties, for example in teaching, and could devote herself entirely to her research. This position was soon converted to a permanent one, and McClintock researched at Cold Spring Harbor well into old age.

In 1944, McClintock was inducted into the US National Academy of Sciences - the third woman in the history of that institution. In the same year, during a guest stay with George Beadle at Stanford University, she established the cytogenetics of the mold Neurospora crassa by finding out how its chromosomes could be differentiated, and for the first time described the meiosis (reduction division) of this organism, which was previously unknown in fungi was. In 1945 she was the president of the Genetics Society of America ; In this one-year position, she was the first woman ever.

McClintock also began in 1944 with the investigations that should lead to the discovery of the "jumping genes" ( transposons ). Initially, it was about spontaneous breaks in chromosome 9 of the maize plant. McClintock observed that chromosome 9 often breaks at a specific point that she called Ds (dissociator). During further investigations in 1948 she came to the surprising result that Ds can change its position on the chromosome. This was the first time she had discovered a transposon - one of the most important causes of spontaneous mutations - and several more were to follow.

Multi-colored corn on the cob

McClintock also found that transposons such as Ds can cause unstable mutations by jumping to locations on the chromosome that are e.g. B. contain a gene for the production of a pigment . By the insertion ( insertion ) of the transposon, the affected Pigmentgen inoperative. This mutation is reversible, however, as there is a certain probability that the transposon “jumps” again, thereby restoring the pigment gene to its functional state. The result is piebald corn kernels or even completely piebald plants. Building on these findings, McClintock developed a general theory of gene regulation and cell differentiation , which she first published in 1950 and then presented at the Cold Spring Harbor Symposium in 1951. In doing so, it contradicted the prevailing notion of a static genome , and its representation was also very complicated. The reactions of colleagues ranged - as she herself later said - from confusion to outright rejection, and some of the articles that followed in various magazines also had little positive response. After 1953 she published very little on this topic, while she continued her research undiminished and documented it in a form suitable for publication.

It is said of the renowned geneticist Alfred Sturtevant that, when asked about McClintock's lecture in 1951, he said: “I didn't understand a word, but if Barbara says that, it must be true.” In 1983 McClintock's biographer Evelyn Fox Keller came to the conclusion that she “ would certainly have been able to convince her colleagues, on the one hand, if she hadn't packed too many facts into her short lecture [which lasted over two hours] and, on the other hand, had better structured it cytogenetics, as practiced by McClintock, and in general, classical genetics based on cross-breeding experiments lost much of its importance. Instead of maize and Drosophila , bacteria and bacteriophages (bacteria infecting viruses ) became the most important objects of investigation, in which no crossings take place and the microscope was no longer used because of their small size. Until the 1940s it was unclear whether bacteria even have genes, and proteins were assumed to be the genetic material , not the supposedly very simply constructed DNA , which only consists of four different building blocks ( nucleotides ). But in 1952 Alfred Hershey and Martha Chase found out in Cold Spring Harbor that bacteriophages only inject their DNA into the bacteria, while their protein content remains on the outside (see Hershey Chase experiment ). This proved that, at least in the case of phages, DNA is the genetic material. The following year, James Watson and Francis Crick clarified the actually very complex structure of DNA ( double helix ).

In his biography The Tangled Field 2001, the historian Nathaniel C. Comfort described the narrative, mainly represented by Keller and partly going back to McClintock himself, that her discovery of the transposons was not accepted in the early 1950s and was only awarded 30 years later the Nobel Prize has been recognized as a "myth". As he explains, the existence of transposable elements in maize was well accepted, independently confirmed by two other scientists, and was already a recognized fact in the mid-1950s. For McClintock, however, transposition was only a minor aspect of their new theory of gene regulation, and it was this broad and very complex theory that met with little interest and understanding.

When McClintock first introduced her theory of gene regulation in 1950/51, she did not expect to be met with much understanding. She was convinced that colleagues needed to be “shaken awake” and saw her contributions as a first step. With another article in 1953, she hoped to provide decisive evidence and thus convince the professional world, but this did not happen. Although she did not publish anything about it in major journals afterwards, she gave lectures and seminars at various universities, and her results found their way into textbooks. After François Jacob and Jacques Monod published their groundbreaking operon model of gene regulation in bacteria (Nobel Prize 1965) in 1960 , McClintock drew attention to similarities with their earlier results in maize in 1961. The fact that she continued to enjoy a high reputation is shown by the fact that she was presented with the Kimber Genetics Award , the highest honor specifically for geneticists at the time, in 1967.

Indigenous maize varieties in Latin America

In 1957, McClintock was asked to contribute her qualification as a cytogeneticist to a project organized by the National Academy of Sciences and the National Research Council to study ancient Latin American varieties of maize. Initially, it should only be a matter of instructing one of the scientists in Peru's facilities in cytogenetics. From this, however, it turned out that, in addition to her research in Cold Spring Harbor, she examined the chromosomes of numerous collected samples of old maize varieties in winter in research facilities from Mexico to Brazil and also gained information about their evolution.

The Nobel Prize and its history

From the late 1950s, the notion of a static genome in bacteria and bacteriophage was modified by the discovery of exceptions. An important discovery was that some bacteriophage can be integrated into their host's chromosome (see lysogenic cycle ). An integrated phage is called a prophage because it is inactive but can become active again by exiting the host chromosome. It was also found that phages can transfer bacterial genes from one bacterium to another ( transduction ). In addition, it turned out that some plasmids (small circular DNA molecules that are present next to the larger chromosome and also contain genes) can be integrated into the chromosome; they are called episomes .

In the early 1960s, some researchers referred to McClintock's work on transposition. Thus , when Allan Campbell postulated in 1962 that prophages are integrated into the host chromosome, a comparison was made with McClintock's transposons in maize. In 1961, doctoral student Austin Lawrence Taylor discovered a phage, which he later named Mu, which integrates into the host chromosome and causes mutations (hence the name Mu). After his doctorate he worked at Demerec, who introduced him to McClintock. During this time, Taylor found that Mu apparently randomly integrated into different parts of the chromosome, causing different mutations. He discussed it with McClintock, who was very interested. As a result, he pointed out McClintock's transposons in his 1963 publication as being comparable.

In 1965 Melvin M. Green first discovered a transposon in Drosophila . In contrast to McClintock's transposons in maize, it was a complete gene that jumped from one chromosome to another. He discussed his results with McClintock and published a paper in 1967 in which he described four such "jumping genes" and quoted McClintock. To his surprise, there was very little interest. McClintock said that the time was not yet ripe for it.

Also in 1967, two working groups independently published a new type of mutation in bacteria. These altered the expression of operons (groups of functionally related genes) and they were reversible. It turned out that these mutations were due to a piece of DNA inserting into one of the genes. In the years that followed, other such mutations were found in various operons, and the inserting DNA pieces were given the name insertion sequence or IS element. Here, too, possible matches with McClintock's transposons in corn were noted. In the 1970s, the role of IS elements in the transmission of antibiotic resistance between bacteria was revealed.

In 1974 the Annual Review of Genetics published an article on the transposons discovered by McClintock in corn. In 1976 she was nominated for the first time - unsuccessfully - for the Nobel Prize in Physiology or Medicine . In 1980 the annual Cold Spring Harbor Symposium was devoted to Movable Genetic Elements in bacteria, viruses, yeast , plants and Drosophila . Transposons were established as an important research area.

Barbara McClintock at her 1983 Nobel Prize speech in Stockholm

In 1981 McClintock received a number of prestigious awards. She became an honorary member of the Society for Developmental Biology , received the first-ever Thomas Hunt Morgan Medal , the $ 50,000 Wolf Prize in Medicine, the $ 60,000 MacArthur Fellowship, and the Albert Lasker Award for Basic Medical Research . In addition, she was nominated again for the Nobel Prize, which she did not receive.

After another unsuccessful nomination in 1982, which was supported by many eminent scientists, she finally received the award in 1983. The number of previous nominations was small compared to other award winners, and it was also unusual that she received the award alone and did not have to share . In this regard, she was the third woman in the history of the Nobel Prize after Marie Curie (1911, chemistry) and Dorothy Crowfoot Hodgkin (1964, chemistry).

Role in the women's movement

In the late 1970s, historians and journalists began taking an interest in McClintock and soliciting interviews. One of them was Evelyn Fox Keller, who published an article in Science in 1981 based on interviews with McClintock and colleagues Beadle, Rhoades, Creighton, and others . In 1983, a few months before the Nobel Prize was awarded, her biography A Feeling for the Organism followed . The book found many readers, and McClintock became a popular example for women scientists disadvantaged because of their gender. But Keller went further, describing McClintock's scientific approach as opposed to the “masculine” established science. The former is holistic , intuitive and interactionistic in contrast to the dominant , rational and reductionist approach of the mainstream. McClintock does not press the facts into logical schemes, but let nature speak to itself. This fit with the thesis that women think fundamentally differently from men, who the psychologist Carol Gilligan in her 1982 book In a Different Voice (German: The other voice ) and many other authors represented. Keller's McClintock biography became the main case study for this view, but neither Keller nor McClintock agreed with it. Keller advocated a science in which gender should not play a role, and McClintock opposed its being appropriated as an icon of feminism .

Last years and death

McClintock found the media attention she received from the awards, above all, as a burden. She continued to take an active part in the annual Cold Spring Harbor symposia and followed the relevant specialist literature. On her 90th birthday, which was celebrated at the home of James Watsons , the director of Cold Spring Harbor Laboratories, the book The Dynamic Genome was published in honor of McClintock. Co -editor Nina Fedoroff read the book's foreword and table of contents at the celebration, and she later wrote that McClintock called the party the best of her life. A few months later she died.

Namesake

After her death, a street in Berlin was named after McClintock. Since 2003 it has given its name to the McClintock Ridge , a mountain ridge in the Antarctic.

Publications (selection)

  • Randolph LF, McClintock B. (1926): Polyploidy in Zea mays L. In: Amer. Naturalist . Vol. 60, pp. 99-102.
  • B. McClintock (1929): Chromosome morphology in Zea mays . In: Science . Vol. 69, p. 629.
  • HB Creighton, B. McClintock (1931): A Correlation of Cytological and Genetical Crossing-Over in Zea Mays . In: Proc. Natl. Acad. Sci. Vol. 17, pp. 492-497. PMID 16587654
  • B. McClintock (1950): The origin and behavior of mutable loci in maize . In: Proc. Natl. Acad. Sci. Vol. 36, pp. 344-355. PMID 15430309
  • B. McClintock (1951): Chromosome organization and genic expression . In: Cold Spring Harb. Symp. Quant. Biol. Vol. 16, pp. 13-47. PMID 14942727
  • B. McClintock (1953): Induction of instability of selected loci in Maize. In: Genetics. Volume 38, 1953, pp. 579-599.
  • B. McClintock (1961): Some parallels between gene control systems in maize and in bacteria . In: Amer. Naturalist . Vol. 95, pp. 265-277.
  • B. McClintock, TA Kato Yamakake, A. Blumenschein (1981). Chromosome Constitution of Races of Maize. Its Significance in the Interpretation of Relationships between Races and Varieties in the Americas. Chapingo, Mexico: Escuela Nacional de Agricultura, Colegio de Postgraduados.
  • B. McClintock (1984): The significance of response of the genome to challenge . In: Science . Vol. 226, pp. 792-801. PMID 15739260

literature

  • Nathaniel C. Comfort: The real point is control: The reception of Barbara McClintock's controlling elements. In: Journal of the History of Biology. 32 (1999) PMID 11623812 , pp. 133-162.
  • Nathaniel C. Comfort: From controlling elements to transposons: Barbara McClintock and the Nobel Prize. In: Trends in Biochemical Sciences . 26 (2001), PMID 11440859 , pp. 454-457. ( PDF )
  • Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed. Harvard University Press, Cambridge, Massachusetts 2003.
  • Nina V. Fedoroff : Jumping genes in maize. In: Spectrum of Science. August 1984, pp. 36-47.
  • Nina V. Fedoroff: Barbara McClintock. In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235. ( PDF )
  • Nina V. Fedoroff, David Botstein (Eds.): The Dynamic Genome: Barbara McClintock's Ideas in the Century of Genetics. Cold Spring Harbor Laboratory Press, Plainview, NY 1992, ISBN 0-87969-422-X .
  • Kendall Haven, Donna Clark: 100 Most Popular Scientists for Young Adults: Biographical Sketches and Professional Paths , Libraries Unlimited, Englewood 1999, ISBN 978-1-56308-674-8 , pp. 336-340
  • RN Jones: McClintock's controlling elements: the full story . In: Cytogenetics Research. 109 (2005), PMID 15753564 , pp. 90-103. ( PDF )
  • Evelyn Fox Keller : A Feeling for the Organism. WH Freeman & Co., New York 1983.
    • German: Barbara McClintock. The discoverer of jumping genes. Birkhäuser Verlag, Basel et al. 1995, ISBN 3-7643-5013-X .
  • Renate Ries: Life is much more wonderful than science lets us know. In: Charlotte Kerner : Not only Madame Curie - women who got the Nobel Prize. Beltz Verlag, Weinheim / Basel 1999, ISBN 3-407-80862-3 .
  • Sigrid Schmitz: Barbara McClintock. 1902-1992. In: Ilse Jahn , Michael Schmitt (eds.): Darwin & Co. A history of biology in portraits. Volume 2. CH Beck, Munich 2001, ISBN 3-406-44639-6 , pp. 490-506.

Web links

Commons : Barbara McClintock  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Evelyn Fox Keller : Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 35-43.
  2. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 43-53.
  3. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 23-27.
  4. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 49-51.
  5. ^ Nina V. Fedoroff : Barbara McClintock . In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235, here p. 216 f. ( PDF )
  6. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 51-54.
  7. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 53.
  8. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 55 f.
  9. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 70-73.
  10. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 77-83.
  11. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 56-60.
  12. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 60-62.
  13. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 85-90.
  14. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 91-97.
  15. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 63-65.
  16. ^ Nina V. Fedoroff: Barbara McClintock . In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235, here p. 220 f. ( PDF )
  17. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 117-120.
  18. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 65 f.
  19. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 122–126.
  20. ^ Nina V. Fedoroff: Barbara McClintock . In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235, here p. 222 f. ( PDF )
  21. ^ RN Jones: McClintock's controlling elements: the full story . In: Cytogenetics Research. 109 (2005), PMID 15753564 , pp. 90-103. ( PDF )
  22. ^ Nina V. Fedoroff: Barbara McClintock . In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235, here pp. 223-225. ( PDF )
  23. ^ Nina V. Fedoroff: Barbara McClintock . In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235, here p. 225 f. ( PDF )
  24. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 165.
  25. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. p. 163.
  26. ↑ Evelyn Fox Keller: Barbara McClintock. The discoverer of jumping genes. Birkhäuser, Basel 1995. pp. 159-175.
  27. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 1-9 and 166-172.
  28. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 158, 166 and 172 f.
  29. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 181-183.
  30. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 205-207.
  31. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 176 f.
  32. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 209-217.
  33. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 227.
  34. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 228 f.
  35. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 230 f.
  36. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 233-237.
  37. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 241-244.
  38. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, p. 245.
  39. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd Ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 246-252.
  40. ^ Nathaniel C. Comfort: The Tangled Field. Barbara McClintock's Search for the Patterns of Genetic Control. 2nd ed., Harvard University Press, Cambridge, Massachusetts, 2003, pp. 4-8.
  41. ^ Nina V. Fedoroff : Barbara McClintock . In: Biographical Memoirs of the National Academy of Sciences. 68 (1995), pp. 211-235, here pp. 229-231. ( PDF )
  42. ↑ neue-strassen.de: Barbara McClintock Strasse in Berlin
personal data
SURNAME McClintock, Barbara
BRIEF DESCRIPTION American geneticist and Nobel Prize winner
DATE OF BIRTH June 16, 1902
PLACE OF BIRTH Hartford , Connecticut
DATE OF DEATH 2nd September 1992
Place of death Huntington , New York
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