Elements causing male crossing over in Drosophila melanogaster.

A second chromosome line of Drosophila melanogaster (Symbol: T-007) has previously been shown to be responsible for the induction of male recombination. In the present investigation, the genetic elements responsible for this phenomenon have been partially identified and mapped. A major element (Symbol: Mr, for Male recombination) locates on the second chromosome between the pr (2L-54.4) and c (2R-75.5) loci and is responsible for the large majority of male recombination. In addition, there appear to be "secondary elements" present which have the ability to induce male recombination in much reduced frequencies and which are diluted out through successive back-cross generations when Mr is removed by recombination. The possible nature of these "secondary elements" is discussed.