Barbara McClintock was born June 16, 1902, in Hartford, Connecticut, one of four children of Thomas Henry McClintock and Sara Handy McClintock. Her family moved to Brooklyn, New York, in 1908. She graduated from Erasmus Hall High School in 1919. McClintock earned her B.S. and M.S. degrees in botany at Cornell University, and received her Ph.D. 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 Dr. McClintock to pursue genetics research at several different 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.

McClintock returned to Cornell for several more years until, in 1936, she 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 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.

McClintock died at Huntington Hospital, near Cold Spring Harbor, on September 2, 1992, at the age of 90.