Unstable chromosome rearrangements associated with male recombination in Drosophila melanogaster.

The male recombination second chromosome 23.5 MRF isolated from the same Greek natural population with the second chromosome 31.1 MRF induced high frequencies of chromosome rearrangements, including specific deletions and duplications. A number of the duplications recovered were found to be highly unstable. The duplicated chromosome segments of the unstable duplications had been either completely or partially lost. The loss occurred most probably by excision of the corresponding segments and not by unequal crossing-over involving sister chromatids. As regards the unstable deletions, they became either shorter or longer or they showed complete restoration. Hypotheses explaining the high frequencies of the unstable chromosome mutations detected are discussed.