Locus of Drosophila Melanogaster

I N a previous paper (LIFSCHYTZ and FALK 1969b) we showed that by using the specific interaction pn-K-pn (prune--Killer-prune) we could construct an efficient screening system in which the products of reversions in the p n and K-pn loci were the only viable male-progeny. The few female progeny that survived served for estimating the number of tested zygotes. K p n is a dominant mutant, interacting with p n to give a hizhly specific and most efficient lethal effect; it is located at the extreme right end of chromosome 3 of Drosophila melanogaster ( STURTEVANT 1956). It is impossible to cancel the interaction by introducing into the genotype, besides p n and K-pn, additional markers which affect pteridine metabolism ( STURTEVANT 1956). Little is known about the mechanism of action of dominant mutants. The fact that K-pn is a “conditional dominant lethal’’ offers an opportunity to study the nature of such a gene. In the present study we tried to clarify the properties of the K p n locus by genetic analysis, i.e. by an analysis of the spontaneous and induced reversions of the K-pn effect.