Barbara McClintock and the transposition concept.

Barbara McClintock was awarded Nobel Prize in Physiology or Medicine in 1983 for the discovery and characterization of jumping genes or transposons. In 1948 she described for the first time maize controlling elements. She proposed 'transposition' as a mechanism that relates phenotypic characteristics with the presence of unstable genes. This discovery was 'ignored' even though she was recognized as a brilliant cytogeneticist. In this paper I approach the matter of the maize research groups within which McClintock developed all of her work, and the problem of variegation in relation to unstable genes and transposition.