Background

Barbara McClintock was born Eleanor McClintock on June 16, 1902, in Hartford, Connecticut, United States to the family of a homeopathic physician Thomas Henry McClintock and Sara Ryder Handy. She was the third of four children. When she was a young girl, her parents decided that the name Eleanor, a "feminine" and "delicate" name given McClintock at birth, was not suitable for her, and chose Barbara instead. McClintock took great pleasure in science as a child and evidenced early the independence of mind and action that she would exhibit throughout the rest of her life. Her family had little money, so her interest in research was viewed with skepticism. It was more important for her to marry, her family thought. Despite this, with her father's support, Barbara began studying. Her family moved to Brooklyn, New York, in 1908.

Education

Barbara McClintock graduated from Erasmus Hall High School in 1919. She earned her Bachelor of Science and Master of Science degrees in botany at Cornell University and received her Doctor of Philosophy in the same subject at Cornell in 1927. Although women were not permitted to major in genetics at Cornell, she became a highly influential member of a small group who studied maize (corn) cytogenetics, the genetic study of maize at the cellular level.

In the early 1930s, prestigious postdoctoral fellowships from the National Research Council, the Guggenheim Foundation, and others, enabled McClintock to pursue genetics research at several institutions, including Cornell, the University of Missouri, and the California Institute of Technology. Part of this postdoctoral training included six months in Germany in 1933-1934, but mounting political tensions across Europe forced her to return to the United States earlier than she expected.

Career

In 1927-1931 Barbara McClintock was an Instructor in Botany at Cornell University. After her postdoctoral studies in 1936, McClintock accepted a position as an assistant professor at the University of Missouri at Columbia from the influential maize geneticist Lewis Stadler. By 1940, however, she believed that she would not gain tenure at Missouri, and left her job. In December 1941, she was offered a one-year research position at the Carnegie Institution of Washington's Department of Genetics at Cold Spring Harbor on Long Island, New York. This job turned into a full-time staff position the following year. In 1967, after 26 years of committed research, McClintock retired from the Carnegie Institution, which awarded her a Distinguished Service Award. She was invited to stay at the Cold Spring Harbor Laboratory as a research scientist. She remained affiliated with the laboratory until her death in 1992.

Throughout her long and distinguished career, McClintock's work focused on the genetics of maize and, in particular, the relationship between plant reproduction and subsequent mutation. Beginning in the late 1920s, she studied how genes in chromosomes could "move" during the breeding of maize plants. She did groundbreaking research on this phenomenon, where she determined the physical correlate of genetic crossing-over. Later, during the 1940s and 1950s, McClintock showed how certain genes were responsible for turning on or off physical characteristics, such as the color of leaves or individual corn kernels. She developed theories to explain the suppression or expression of genetic information from one generation of maize plants to the next that defied the common wisdom of molecular biology prevalent during the 1950s. After encountering some skepticism about her research and its implications, she refrained from publishing her data in professional journals and only shared her research with a small circle of loyal colleagues.

In 1957, McClintock received funding from the National Science Foundation and the Rockefeller Foundation to study different varieties, or races, of maize in South and Central America. In the early 1960s, she traveled extensively, collected maize samples that demonstrated interesting evolutionary characteristics, and mentored junior scientists and young graduate students in maize genetics. McClintock and her colleagues spent two decades assembling data on differences in South American maize, which were finally published in 1981 as The Chromosomal Constitution of Races of Maize.

McClintock also was an Andrew D. White Professor-at-Large at Cornell University from 1965 until her retirement in 1974.

Achievements

• Barbara McClintock was recognized throughout her career as one of the most distinguished scientists of the 20th century. In 1944, she became the third woman elected to the National Academy of Sciences. She was the first woman to become president of the Genetics Society of America, to which she was elected in 1945. In 1971, President Richard M. Nixon awarded McClintock the National Medal of Science.
  
  In 1981, McClintock became the first recipient of a MacArthur Foundation Grant, now known informally as the "genius" grant, which was awarded for her lifetime. In that same year, she was given the Albert and Mary Lasker Award. In 1983, at the age of 81, she received the Nobel Prize in Physiology or Medicine for her work on "mobile genetic elements," that is, genetic transposition, or the ability of genes to change position on the chromosome. McClintock was the first woman to receive an unshared Nobel Prize in that category.

Works

More photos

• book

  • The Discovery & Character of Transposable Elements 1987

Religion

McClintock had little patience for religion and its offerings of mental comfort.

Politics

McClintock hated politics and preferred to stay uninvolved.

Views

Beginning in 1944 Barbara McClintock studied the relationship between color patterns on corn plants and the look of their chromosomes. One of the colors she was most interested in was purple. She wanted to understand the genetic reasons for purple-spotted corn. The corn plants from one generation to the next were self-pollinated. Comparing offspring with parent chromosomes, she found it looked like the offspring chromosomes were reorganized versions of parent chromosomes. Parts of the chromosomes looked like they had been snipped out and shifted to entirely new locations. She discovered parts of the chromosome - she called them Dissociators (Ds) and Activators (Ac) – that could cause insertions, deletions, and relocations of genes in the chromosome.

The theory of the time said genes were in fixed positions on the chromosome: McClintock’s work showed this was wrong. The Dissociator could break the chromosome and alter the behavior of genes around it, but only in the presence of the Activator. The purple color could be switched on or off by the Dissociator. In other words, physical traits were being controlled by Dissociators and Activators. In 1948, she discovered that Dissociators and Activators could transpose - in other words, jump to different places on the chromosome. They are often, therefore, called transposable elements.

McClintock produced a theory that the Dissociators (Ds) and Activators (Ac) were in fact gene controllers - she called them controlling elements. They controlled the genes on a chromosome – they could inhibit or modify their behavior. This explained why an individual living thing, such as a person, can produce all sorts of different cells even though every cell has the same genetic code. The gene controllers make the difference by giving specific instructions in specific circumstances.

In McClintock’s view, genes could no longer be thought of as unchangeable instructions handed from parents to offspring. They could react to specific circumstances in the environment. Mobile genes could jump around within chromosomes and switch physical traits on or off. She studied this phenomenon until 1950 before she began publishing her work. In a scientific world that believed genes were very stable and could only change a little at a time, her findings were so radical that she was worried about how people would react to them.

Soon after McClintock presented these findings at a symposium in 1951, she stopped publishing her work, so disappointed was she at its reception. Furthermore, the discovery of the double helix structure of DNA in 1953 turned many geneticists away from the "old-fashioned" technique of McClintock (careful experiment, observation, and recording) to the more mechanistic models of James Watson, Francis Crick, and their associates. Partly because of her solitary nature, but also partly because she wanted to stay in close touch with her experiments, McClintock chose to work alone rather than as part of a large research team. As a result, she was in physical and intellectual control of all aspects of her work. As one colleague put it, she had a feeling for the organism.

A deeply private person, McClintock continued to pursue her work alone and with the same holistic perspective she used throughout her career. Although the basics of her experimental work were not only accepted but honored, some of her larger hypotheses were yet to find an audience.

Membership

Barbara McClintock was a member of the National Academy of Sciences, the American Academy of Arts and Sciences, the American Philosophical Society, the American Association for the Advancement of Science, the Royal Society, the Genetics Society of America, the Genetics Society of America, and the American Society of Naturalists.

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  National Academy of Sciences , United States

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  American Academy of Arts and Sciences , United States

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  American Philosophical Society , United States

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  American Association for the Advancement of Science , United States

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  Royal Society , United Kingdom

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  Genetics Society of America , United States

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  American Society of Naturalists , United States

Personality

Enthusiastic, intense, dedicated, and shy, McClintock was a very private person in what became her very public world. While not working in the field that won her renown, she enjoyed playing the banjo, studying Eastern religions and forms of meditation, and while she worked in Cold Spring Harbor accompanying the local children home from the school bus speaking to them about nature. Her closest friends believed her mystical insight and "touch of genius, alloyed with sheer grit, determination and tenacity" made her "short in size, but great in stature" in a field that did not gladly receive women.

Interests

• Eastern religions

Connections

Barbara McClintock never had a husband and children.

Father:

Thomas Henry McClintock

Mother:

Sara Ryder Handy

Friend:

Marcus Morton Rhoades

Friend:

George Beadle

References

• Barbara McClintock: Nobel Prize Geneticist
  2012
• Barbara McClintock: Cytogeneticist and Discoverer of Mobile Genetic Elements
  2017
• Barbara McClintocK: Alone in Her Field
  2016
• The Dynamic Genome: Barbara McClintock's Ideas in the Century of Genetics
  1992