Abstract
Summary: The three major regions (T, tail-determining; A, abnormal transmission ration; L, embryonic lethality) of thetcomplex on the murine seventeenth chromosome can interact to influence male reproduction (Lyon & Mason, 1977; Hammerberg, 1981). Evidence is presented here that suggests: (1) the presence of a polymorphic system within the T region that influences quasi-sterility in the male; (2) the existence of enhancing factors of transmission ratio distortion; and (3) that preferential interactions betweent-haplotypes are found to occur bothcisandtranswhich influence transmission ratio distortion.