Genetic instability in Drosophila melanogaster: the genetics of an MR element that makes complete P insertion mutations.

An MR element that maps to a specific locus in chromosome 3 of Drosophila melanogaster has the unusual feature of producing complete P (a mobile element) sequence mutations at several X chromosome loci. This MR also increases the frequency of mitotic recombination. Evidence is given for the transposition of MR. The complete P insertion mutations are autonomously unstable and are capable of causing otherwise stable incomplete (defective) P insertion mutations to revert. These results complement the analysis of P element functions with a synthetic complete P derivative. The genetic basis for the mutational-mitotic recombinational components of "hybrid dysgenesis" is conveniently explicable in terms of MR elements present in the genomes of flies present in the wild.