Segregation Distorter Stocks

Segregation Distorter is a genetic system in which males heterozygous for a SD second chromosome and a Rsp-sensitive homolog transmit the SD chromosome to greater than 50% of progeny, a phenomenon known generally as meiotic drive. Factors on the SD chromosome induce a failure of chromatin condensation in haploid spermatids receiving the Rsp-sensitive homolog.

SD chromosomes from nature carry a dominant, gain-of-function mutation in RanGAP called RanGAP[Sd]. They also carry dominant alleles of M(SD), E(SD) and St(SD), which strengthen the SD effect. Homologous second chromosomes susceptible to the SD effect carry a sensitive version of the Responder (Rsp) locus, a region of heterochromatin consisting of 120 bp A-T rich repeats. The number of repeats correlates with the degree of sensitivity, which ranges from insensitive (Rspi) through sensitive (Rsps) to supersensitive (Rspss). SD chromosomes from nature are Rsp-insensitive, while wild type chromosomes can be Rsp-insensitive, -sensitive or -supersensitive.