Studies on the sex-specific lethals of Drosophila melanogaster. IV. Gynandromorph analysis of three male-specific lethals, mle, msl-2(27) and mle(3)132.

Mutants at three male-specific lethal loci of Drosophila melanogaster (mle, msl-2(27) and mle(3)132) were examined by gynandromorph analysis. In all cases only a very few gynandromorphs with small X/O patches appeared. Most of these small X/O patches were in the abdomen, and the structures in these X/O regions were reduced in size. These results indicate that the primary effects of these mutants are not on any particular organs or tissues, but rather on individual cells, mle and msl-2 have been shown by BELOTE and LUCCHESI (1980a) to be defective in dosage compensation in X/Y males. We suggest that this dosage-compensation defect results in the expression of Minute-like phenotypes in X/O cells, and hence results in the death of X/O males and flies with large X/O tissue areas.