A jumping sex determining factor in the fly Megaselia scalaris

To test earlier reports on changes of the sex determining linkage group in Megaselia scalaris, we used a combination of a cytogenetic and a phenotypic marker in a laboratory strain as a detection system for rare cases in which linkage of the marker and the Y chromosome was disrupted. From some of the exceptional males detected in this system we established strains with a different chromosome pair acting as the sex chromosome pair. Cytogenetic analysis, crossbreeding tests with a phenotypic marker and DNA blot hybridization with cloned DNA probes indicated that an epistatic male determining factor had moved to one of the former autosomes at a frequency of at least 0.06%.