Evidence for Two Regions in the MousetComplex Controlling Transmission Ratios

Abstract

SUMMARY: Four newthaplotypes,t^Tu1throught^Tu4, are described, three of them derived from thet^w12tfhaplotype and one (t^Tu4) from thet^w2haplotype. Thet^Tu1andt^Tu4haplotypes cause taillessness inT/t^Tu1orT/t^Tu4heterozygotes, lack the lethality factor, weakly suppress recombination in theT−H−2interval, and are transmitted to offspring fromt^Tu/+ males at nearly Mendelian ratios. Thet^Tu3haplotype resemblest^Tu1andt^Tu4except for the fact that theT/t^Tu3heterozygotes have normal-length tails. Thet^Tu2haplotype probably carries the lethal factor oft^Tu12tf, suppresses crossing-over in theT-H-2andtf-H-2intervals, and displays a slightly subnormal transmission ratio. In the compound heterozygotet^Tu1/t^Tu2, the male transmission ratio of thet^Tu1chromosome is close to that of the originalt^Tu12tfhaplotype. A similar effect is observed in thet^Tu3/t^Tu2heterozygote. This observation is interpreted as evidence for two regions within thetcomplex controlling the male transmission ratios. One of the regions is close to the tail-modifying region, the other is close to the lethality factor. Our findings parallel closely those made in the segregation distorter system inDrosophila.