ABSTRACT
Barbara McClintock began her studies at Cornell University’s College of Agriculture in 1919, receiving a BSc in Biology in 1923. She developed the technique for visualizing maize chromosomes and, by using microscopic analysis, demonstrated genetic recombination and crossing over during meiosis, preparing the first genetic map for maize, linking regions of the chromosome to physical traits. While working with the geneticist Lewis Stadler at Missouri University during the summers of 1931 and 1932, McClintock was introduced to the use of X-rays as a mutagen. She showed that the loss of ring-chromosomes at meiosis caused variegation in maize foliage in generations subsequent to irradiation resulting from chromosomal deletion. In 1931, McClintock published the first genetic map for maize, showing the order of three genes on maize chromosome 9. McClintock’s classic paper on the characterization of triploid maize chromosomes triggered wide interest in maize cytogenetics among biologists.
