Meiotic drive of t haplotypes: chromosome segregation in mice with tertiary trisomy

The properties of the t haplotypes, specific mutant states of the proximal region of chromosomes 17 in the house mouse, are of continuing interest. One such property is increased transmission of the t haplotype by heterozygous t/+ males to offspring. Using the reciprocal translocation T(16;17)43H we have constructed males with tertiary trisomy of chromosome 17 (+T43/+ +/Rb7+) carrying the Robertsonian translocation Rb(16.17)7Bnr. Only the progeny of these males which had inherited either T43/+ or Rb7 from their male parent were viable. The segregation patterns in the offspring of t-bearing trisomics were analysed on days 16-18 of embryonic development. It was found that, when the t12 haplotype is in the normal acrocentric (males+ +T43/+ t12 + /Rb7+ +), its presence in the gamete +t12+/+ + T43 does not produce meiotic drive. However, when t6 is in Rb7, meiotic drive was observed: 80% of offspring carried the t haplotype. It is concluded that the meiotic drive is probably inhibited by the presence of a normal homologue of chromosome 17 in the same sperm. Possible mechanisms for the t haplotype effect are discussed.