PARAMETERS OF SPONTANEOUS AND X-RAY-INDUCED REVERSION OF WHITE-IVORY MUTANT OF DROSOPHILA

The white-ivory mutant of Drosophila melanogaster reverts frequently to wild type both in germinal and somatic cells. Spontaneous germinal reversion is restricted to meiosis and is dependent on synapsis with a structurally normal homologue. Reversion in mitotic cells, both premeiotic germinal and somatic, shows no such restriction and is, furthermore, greatly enhanced by X-irradiation. In somatic cells, the frequency of induced reversion is a linear function of the X-ray dose. The effectiveness of X-rays is, however, much greater in somatic than in premeiotic germ cells. The properties of the white-ivory mutant suggest that it is the result of the addition of genetic material to the white locus although the nature of this addition remains an intriguing mystery. © 1969.