MAPPING A MUTATOR, MU2, WHICH INCREASES THE FREQUENCY OF TERMINAL DELETIONS IN DROSOPHILA-MELANOGASTER

A mutator, mu2, in Drosophila melanogaster has been identified recentl y that potentiates the recovery of terminal deficiencies. The deleted chromosomes behave as if they had been capped; that is, they are prote cted from degradation and from fusion with other chromosome fragments. The mutator maps near the telomere on the left arm of chromosome 3. U sing the selectable marker Aprt, 150 deficiencies for region 62 of the cytological map have been recovered. These deficiencies identify the map position of mu2 as 62B11-C1. A yeast artificial chromosome spannin g this region has been subcloned into lambda phage, and the positions of deficiency breakpoints on either side of the mu2 gene have been ide ntified within the subclones. These positions limit the location of th e left end of the gene to a 23 kb region. In the course of these exper iments, three additional, presumptive mutant alleles were identified, suggesting that other mutator alleles remain undiscovered in many stan dard laboratory stocks.