DROSOPHILA P-ELEMENT TRANSPOSASE INDUCES MALE RECOMBINATION ADDITIVELY AND WITHOUT A REQUIREMENT FOR P-ELEMENT EXCISION OR INSERTION

P element dysgenesis-associated male recombination in Drosophila was e xamined with a selective system focused upon a section of the third ch romosome divided into eight recombination segments. Tests compared cro ssing over in the presence of none, one and two doses of P(Delta 2-3) (99B), a non-mobile transposase source, in the absence of a mobilizabl e P element target in the genome. In the presence of the P transposase source, and without a P element target, significant male recombinatio n occurred in genomic regions physically separated from the P(Delta 2- 3) site. Using two doses of P(Delta 2-3) without a P element target, t he male recombination rate doubled, and 90% of the crossovers occurred in the pericentric region. The distribution of recombination events, in the absence of P element targets approximates that seen in studies of radiation induced mitotic crossing over and the metaphase chromosom e map. Another experiment examined the effects of one dose of P(Delta 2-3) on a genome with a Single P element target, P(lArB) (87C9), in th e third recombination segment. Crossovers increased 58-fold in the imm ediate region of the P element target.