Excerpt:
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.