Barbara McClintock (1902-1992), US geneticist, holding a cigarette holder. McClintock worked at the Carnegie Institution at Cold Spring Harbor, New York, USA. She is most famous for her work in the 1940s and 1950s on the genetics of maize. She discovered the moving of genes in chromosomes, by observing patterns of kernel colouration. She named these genes transposable elements. In 1983 she received the Nobel Prize in Physiology or Medicine for her work on mobile genetic elements. Photographed in around 1960 at Cold Spring Harbor, USA.