Evidence for Two Regions in the MousetComplex Controlling Transmission Ratios

Abstract

SUMMARYFour newthaplotypes,tTu1throughtTu4, are described, three of them derived from thetw12tfhaplotype and one (tTu4) from thetw2haplotype. ThetTu1andtTu4haplotypes cause taillessness inT/tTu1orT/tTu4heterozygotes, lack the lethality factor, weakly suppress recombination in theT−H−2interval, and are transmitted to offspring fromtTu/+ males at nearly Mendelian ratios. ThetTu3haplotype resemblestTu1andtTu4except for the fact that theT/tTu3heterozygotes have normal-length tails. ThetTu2haplotype probably carries the lethal factor oftTu12tf, suppresses crossing-over in theT-H-2andtf-H-2intervals, and displays a slightly subnormal transmission ratio. In the compound heterozygotetTu1/tTu2, the male transmission ratio of thetTu1chromosome is close to that of the originaltTu12tfhaplotype. A similar effect is observed in thetTu3/tTu2heterozygote. 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.