The Genetic Basis of Transmission-Ratio Distortion and Male Sterility Due to the t Complex

Abstract

The abnormal transmission ratios observed in male mice heterozygous for a complete t haplotype have been shown by breeding studies to be due to three or more distorter genes acting on a responder gene. The action of the t form of the responder is relatively resistant to this harmful action. When the distorters are homozygous, their harmful action is more severe. The t form of the responder is then affected, and the males are sterile. The distorter and responder genes are distributed over a region occupying the proximal third of mouse chromosome 17. Crossover suppression between t and wild-type bapiotypes in this region is due to the presence of inversions and is thought to be selectively advantageous in locking the genetic factors together. The recessive lethals carried by many t haplotypes are also thought to be advantageous in removing the sterile males from the population. Transmission ratio is also affected by genetic background, and there is evidence of differences among t haplotypes either in the re...