AGENCY FOR TOXIC SUBSTANCES AND DISEASE REGISTRY

Barbara McClintock

Barbara McClintock (June 16, 1902 – September 2, 1992) 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. 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 as among the best in the field, awarded prestigious fellowships, and elected a member of the National Academy of Sciences in 1944.

The McClintock family moved to Brooklyn in 1908 and McClintock completed her secondary education there at Erasmus Hall High School; she graduated early in 1919. She discovered her love of science and reaffirmed her solitary personality during high school. She wanted to continue her studies at Cornell University's College of Agriculture. Her mother resisted sending McClintock to college, for fear that she would be unmarriageable. McClintock was almost prevented from starting college, but her father intervened just before registration began, and she matriculated at Cornell in 1919.

McClintock's cytogenetic research focused on developing ways to visualize and characterize maize chromosomes. This particular part of her work influenced a generation of students, as it was included in most textbooks. She also developed a technique using carmine staining to visualize maize chromosomes, and showed for the first time the morphology of the 10 maize chromosomes. This discovery was made because she observed cells from the microspore as opposed to the root tip. By studying the morphology of the chromosomes, McClintock was able to link specific chromosome groups of traits that were inherited together. Marcus Rhoades noted that McClintock's 1929 Genetics paper on the characterization of triploid maize chromosomes triggered scientific interest in maize cytogenetics, and attributed to her 10 of the 17 significant advances in the field that were made by Cornell scientists between 1929 and 1935.

In 1957, McClintock received funding from the National Academy of Sciences to start research on indigenous strains of maize in Central America and South America. She was interested in studying the evolution of maize through chromosomal changes, and being in South America would allow her to work on a larger scale. McClintock explored the chromosomal, morphological, and evolutionary characteristics of various races of maize. After extensive work in the 1960s and 1970s, McClintock and her collaborators published the seminal study The Chromosomal Constitution of Races of Maize, leaving their mark on paleobotany, ethnobotany, and evolutionary biology.

Most notably, she received the Nobel Prize for Physiology or Medicine in 1983, the first woman to win that prize unshared, and the first American woman to win any unshared Nobel Prize. It was given to her by the Nobel Foundation for discovering "mobile genetic elements"; this was more than 30 years after she initially described the phenomenon of controlling elements. She was compared to Gregor Mendel in terms of her scientific career by the Swedish Academy of Sciences when she was awarded the Prize.

McClintock spent her later years, post Nobel Prize, as a key leader and researcher in the field at Cold Spring Harbor Laboratory on Long Island, New York. McClintock died of natural causes in Huntington, New York, on September 2, 1992 at the age of 90; she never married or had children.