Studies on the sex-specific lethals of Drosophila melanogaster. II. Further studies on a male-specific lethal gene, maleless.

Effects of a second chromosome male-specific lethal gene, maleless (mle), of Drosophila melanogaster were further studied. It was shown that, although no maternal effect was seen with respect to the male-specific lethality, the lethal stage was influenced by whether parental females were homozygous or heterozygous for mle. Thus, in the former mle/mle males died mostly in the late third instar larval stage, while in the latter practically all males survived to the pupal stage. In the dying mle/mle male pupae complete differentiation of adult external head and thorax structures was often observed but that of abdominal structures was incomplete forming only a few segments in most cases. Imaginal discs from third instar mle/mle male larvae which were produced by mle/mle mothers and were destined to die as larvae were able to differentiate into adult structures upon transplantation into normal third instar larval hosts. A somewhat elaborated version of the previously presented hypothesis (FUKUNAGA, TANAKA and OISHI 1975) was discussed as to the possible presence of a class of sex-specific lethals which are not related to the process of primary sex differentiation.