Cytogenetics: in search of the physical basis of gens

Abstract

In 1865 Mendel discovered the existence of constant numerical sequences in the heredity of characteristics in commom peas. In order to explain these observations he suggested to search for a mechanism governing the germinal cells. The hypothetical factors introduced by Mendel, later on termed gens, were considered mere computing units when his work was rediscovered in 1900. A few years later, however, the cytologists W. Sutton and Th. Bobery put forward the hypothesis that the chromosomes were the carriers of the heredity units. The further development of these ideas by T. H. Morgan and coworkers accomplished the consolidation of the chromosomal theory of Mendelian heredity. This research examines the process of locating the gens in the chromosomes and hence their acceptance as material entities, quite different from the abstract computing units meant as tooUs to systematize the results obtained from experimental crossbreeding.