Techniques for manipulating chromosomal rearrangements and their application to Drosophila melanogaster. I. Pericentric inversions.

Techniques have been developed for manipulating pericentric inversions in Drosophila that are based on the lethality of grossly aneuploid zygotes and the existence of recombinationally interconvertible genotypes for any heterozygous inversion complex: males of some of these genotypes will produce only aneuploid sperm, which can be used to rescue complementary aneuploid ova and selectively recover recombinational derivatives of inversions. Markers can be recombined into inversions through a sequence of selected single exchanges, and a novel type of duplication can be synthesized from overlapping inversions that has the characteristics of both insertional and tandem duplications; there are also applications to half-tetrad analyses.--Two cytogenetic screens are developed: (1) the dominant lethality of a large insertional-tandem duplication can be reverted by deletional events that give rise to net deficiencies or duplications, and (2) deficiencies and tandem duplications in proximal regions can be selectively recovered as the results of unequal exchanges within an inversion loop. Recombinants have been recovered between breakpoints separated by distances of as little as fifty bands, arguing against the existence of some small number of sites necessary for the initiation of recombinational pairing. In several instances, hyperploids for four to six numbered divisions were observed to be fertile in both sexes.