IV. Functional units: Introductory remarks

Abstract

During this session we will be considering the question of what constitute the functional units of eukaryotic genomes. In 1928 the plant cytologist Belling proposed that the chromomeres evident in the chromosomes at leptotene of meiosis represent genes, each being a unit of mutation and recombination as well as of function. The beads-on-a-string notion of genomic organization endured for some 20 years. It received powerful support from the great body of cytogenetic work on the cross-banded polytene chromosomes of Drosophilia , following their rediscovery in 1933, which soon led Painter (1934) to declare that by studying these objects we would be led to the ‘lair of the gene’. The beads-on-a-string concept was challenged by Goldschmidt in 1938, it was swept under the carpet during the great postwar surge of microbial and biochemical genetics, and appeared to suffer the coup de grace when the string as well as the beads were shown to contain one continuous duplex of DNA; in other words, all the genomic material is string.