Male recombination with single and homologous P elements in Drosophila melanogaster.

It has previously been shown that, in the presence of a source of P element transposase, male recombination in Drosophila melanogaster is induced at a rate of about 1% in the region of a single P[CaSpeR] element. This paper shows that recombinant chromosomes retain unaltered P[CaSpeR] elements at the original site in a high proportion of cases. This result is incompatible with a simple model in which recombination occurs by resolution of a Holliday junction following P element excision and repair. It has also previously been shown that homozygous regions containing a P element produce male recombination levels of 10-20%, an order of magnitude higher than that given by a single element. This paper shows that reciprocal recombinant chromosomes retaining P[CaSpeR] elements can be combined to produce similarly high levels of recombination. This result potentially allows for recombinant chromosomes from homologous recombination to be analysed at the molecular level in the region of the inserted element.