Genetic analysis of the Om(2D) locus in Drosophila ananassae

The Om(2D)63 mutants were mutagenized by gamma-ray irradiation and DEB feeding. A total of nine revertants were recovered and characterized; eight revertants were homozygous-lethal expressing no appreciable abnormality in cuticular pattern and central nervous system, and all failed to complement the lethality with each other. Two of the eight expressed embryonic lethality and were associated with cytologically detectable deletions including the putative Om(2D) locus, while four were associated with rearrangements in a region distal to the insertion sites of the tom elements. No rearrangement was detected in the remaining two by Southern blot analysis. One of the nine revertants was homozygous-viable with wild-type eyes and was associated with a reciprocal translocation with the break points at 48B in 2R (Om(2D) locus) and 96A in 3R. Based on these data, it is concluded that interaction between the region comprised of a single complementation group of the recessive lethal and the inserted tom elements seems to be responsible for the Om(2D) mutant phenotype. In addition, two induced dominant enhancers specific to Om(2D)63 were identified; both mapped on chromosome 2.