INDUCED SOMATIC AND GERMINAL REVERSION OF THE WHITE-SPOTTED-1 INSERTIONAL MUTANT PHENOTYPE IN DROSOPHILA-MELANOGASTER

The white-spotted-1 (w(spl)) mutant of Drosophila melanogaster is char acterized by the presence of an 8.7 kb retrotransposon (B104) inserted in the regulatory region of the white locus. The frequency of reversi on in both somatic tissue and the germline after exposure to three dif ferent alkylating agents has been analysed. To determine if germinal r evertants were induced by precise excision of the insertional element we analysed several phenotypic revertants using PCR and Southern blot tecniques. The results indicate that, under our experimental condition s, the mutagens used did not induce excision of B104 in the white gene . In addition, the revertant phenotypes obtained were due to the exist ence of second site modifiers acting on expression of white. Such modi fiers map near the white locus and, at least in one case, may correspo nd to suppressor-of-white-spotted.