 Barbara McClintock ( June 16 , 1902 – September 2 , 1992 ) was an American scientist and <unk> who was awarded the 1983 Nobel Prize in Physiology or Medicine . McClintock received her PhD in botany from Cornell University in 1927 . There she started her career as the leader in the development of maize cytogenetics , the focus of her research for the rest of her life . From the late 1920s , McClintock studied chromosomes and how they change during reproduction in maize . She developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas . One of those ideas was the notion of 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 to physical traits . 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 among the best in the field , awarded prestigious fellowships , and elected a member of the National Academy of Sciences in 1944 . 
