Barbara McClintock
1902 – 1992 · United States
Known for: American cytogeneticist who discovered transposable elements, genes that move within the genome
“She listened to the maize until it told her what no theory yet allowed.”
Biography
Barbara McClintock was born Eleanor McClintock on June 16, 1902, in Hartford, Connecticut, the third of four children of a homeopathic physician and his wife, and her parents soon exchanged the name for Barbara, judging the first too delicate for the child they had. From the age of three until she began school she lived with an aunt and uncle in Brooklyn, easing the household finances while her father built his practice, and she later described the result as a capacity to be alone. She finished her secondary education at Erasmus Hall High School in 1919 and wanted Cornell; her mother resisted, fearing that a college daughter would not marry, and her father settled the matter just before registration. A first genetics course in 1921 and an invitation to join the graduate course the following year fixed her direction, and she took her bachelor's degree in 1923, a master's in 1925 and a doctorate in 1927.
At Cornell she helped assemble the group that made maize the central organism of plant cytogenetics. Working with carmine staining and cells taken from the microspore rather than the root tip, she was the first to describe the shape and identity of all ten maize chromosomes, and her papers of the late 1920s drew a generation of researchers into the field. In 1930 she described the cross-shaped pairing of homologous chromosomes during meiosis, and in 1931, with Harriet Creighton, she showed that visible chromosomal crossing over corresponded to the reshuffling of inherited traits. Later, studying patterns of colour in maize kernels, she identified elements that move within the genome and switch genes on and off; met with widespread doubt, she stopped publishing her data in 1953.
She turned to the cytogenetics and ethnobotany of South American maize races and continued her observations quietly. Molecular work in the 1960s and 1970s confirmed the mechanisms she had documented decades earlier, and recognition followed, culminating in the 1983 Nobel Prize in Physiology or Medicine for the discovery of genetic transposition, still the only unshared award to a woman in that category. She died on September 2, 1992, at the age of ninety, leaving behind a genome understood as something mobile rather than fixed.