BICHROMOSOMAL SYNTHETIC SEMILETHALS IN DROSOPHILA PSEUDOOBSCURA

Abstract

A low viability, well in the semilethal range, is found in individuals which carry in duplicate (are homozygous for) a certain 2nd and a certain 3rd chromosomes. In the homozygotes for this 2nd chromosome without the 3rd, and for the 3rd without the 2nd, relatively slight reductions of the viability are observed. Simultaneous homozygosis for both chromosomes thus creates a "synthetic" semilethal. Two further examples are recorded where a 2nd and a 3rd chromosomes, each of which is semilethal in double dose, give a very low viability in the double homozygotes, Epistatic (synergistic) interactions of the components of genetic loads in Drosophila populations appear to be widespread and important.