Spontaneous male recombination and mutation in isogenic-derived chromosomes of Drosophila melanogaster.

Spontaneous male recombination and visible mutations were observed in second and third chromosomes derived from an isogenic line, ID, previously found to exhibit a high recessive lethal mutation rate. All three types of events tend to occur very early in spermatogenesis resulting in large clusters of identical recombinant or mutant progeny from a single male. Mutations and male recombination exchange points tend to be located more frequently in the right arm than in the left in both second and third chromosomes but for a trivial reason in the case of chromosome 2. No significant differences in male or female recombination were found between the progeny of reciprocal crosses. Male recombination in chromosome 2, like recessive lethal mutation, is independent of the presence of ID third chromosomes in the same genome. Both quantitative and qualitative differences in male recombination were found when ID chromosomes were compared with others extracted from natural populations.