Conversion as a possible mechanism of high coincidence values in the centromere region of Drosophila.

Crossing over has been studied with mutants which flank the centromere of chromosome 3 in Drosophila melanogaster. Coefficients of coincidence greater than one were obtained. Putative double crossovers were recovered for genetic intervals whose genetic length is less than one centimorgan. It is suggested that gene conversion rather than conventional double crossing over accounts for the negative interference observed.