Four new t haplotypes, tTu1 through tTu4, are described, three of them derived from the tw12tf haplotype and one (tTu4) from the tw2 haplotype. The tTu1 and tTu4 haplotypes cause taillessness in T/tTu1 or T/tTu4 heterozygotes, lack the lethality factor, weakly suppress recombination in the T−H−2 interval, and are transmitted to offspring from tTu/ + males at nearly Mendelian ratios. The tTu3 haplotype resembles tTu1 and tTu4 except for the fact that the T/tTu3 heterozygotes have normal-length tails. The tTu2 haplotype probably carries the lethal factor of tTu12tf, suppresses crossing-over in the T-H-2 and tf-H-2 intervals, and displays a slightly subnormal transmission ratio. In the compound heterozygote tTu1/tTu2, the male transmission ratio of the tTu1 chromosome is close to that of the original tTu12tf haplotype. A similar effect is observed in the tTu3/tTu2 heterozygote. This observation is interpreted as evidence for two regions within the t complex 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 in Drosophila.
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