Barbara McClintock (June 16, 1902 – September 2, 1992) was a pioneering American scientist and one of the world's most distinguished cytogeneticists. McClintock received her PhD in botany from Cornell University in 1927, where she was a leader in the development of maize cytogenetics. The field remained the focus of her research for the rest of her career. From the late 1920s, McClintock studied chromosomes and how they change during reproduction in maize. Her work was groundbreaking: she developed the technique to visualize maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas, including genetic recombination by crossing-over during meiosis—a mechanism by which chromosomes exchange information. She produced the first genetic map for maize, linking regions of the chromosome with physical traits, and she demonstrated the role of the telomere and centromere, regions of the chromosome that are important in the conservation of genetic information. She was recognized amongst the best in the field, awarded prestigious fellowships and elected a member of the National Academy of Sciences in 1944. (More...)