The regulation of male-specific transcripts by sex determining genes in Drosophila melanogaster.

The accumulation of male-specific transcripts in various genotypes of Drosophila melanogaster was analysed by Northern blot hybridization. The genotypes were either hetero- or homozygous for a mutation in one of the genes for somatic sex determination. The aim was to study the role of these genes in regulating male-specific transcription in soma or germ line. All intersexual phenotypes and pseudomales irrespective of their genotypic sex accumulate the male-specific somatic RNA demonstrating that it is regulated by these genes. In contrast to this, the transcript from the male germ line could only be detected in those mutant genotypes that have the male sex chromosome constitution of X/Y, although its synthesis is not dependent on the presence of a Y chromosome. It is, therefore, not under the control of the sex determining loci but directly regulated by the primary signal for sex determination, namely the ratio of X chromosomes to autosomes.