Barbara McClintock (1902-1992) in 1944 became the third woman elected to the Academy. In the 1940s and 1950s McClintock’s work on the cytogenetics of maize led her to theorize that genes are transposable — they can move around — on and between chromosomes. McClintock drew this inference by observing changing patterns of coloration in maize kernels over generations of controlled crosses. The idea that genes could move did not seem to fit with what was then known about genes, but improved molecular techniques of the late 1970s and early 1980s allowed other scientists to confirm her discovery, and consequently she was awarded the Nobel Prize in Physiology or Medicine in 1983. This made McClintock the first American woman to win an unshared Nobel. McClintock was born in Hartford, CT, and obtained her undergraduate and doctoral degrees at Cornell University’s College of Agriculture. From 1931-1933 she was supported by a fellowship from the National Research Council; from 1941until her death she worked at the Cold Spring Harbor Laboratory in New York. Among the many honors awarded her was the National Medal of Science, the US government’s highest science award, which she received in 1970.