Selective fertilization at the T-locus of the mouse

Advantage was taken of a unique situation to test, with adequate controls, the assertion that male and female gametes conjugate at random. The data concern the aberrant locus T of the mouse, at which there are a number of t alleles that enter into the majority of effective spermatozoa of males heterozygous for one of them. Segregation in females is normal. Evidence is presented for one of these t alleles, tailless-Edinburgh ( t e ), that conjugation between gametes was not at random when this gene was present in spermatozoa. When a choice of eggs was presented by heterozygous females, tailless-Edinburgh spermatozoa united more frequently with normal than with brachyury eggs and more frequently with brachyury than with tailless-Edinburgh eggs. The relevance of this finding is discussed in relation to expected equilibria of t alleles in closed populations. Other forms of selective fertilization are discussed and their genetic consequences compared.