Information on the nature oft-haplotypes from the interaction of mutant haplotypes in male fertility and segregation ratio

Abstract

SUMMARY: Thet-haplotypet⁶interacts with brachyury,T, to produce taillessness, and exhibits lethality, male sterility and high male segregation ratio. Mutant haplotypes derived fromt⁶which have lost the lethality also lose the sterility. We here report that two mutants which have retained the lethality have also retained the sterility and suggest that the two properties of lethality and sterility are due to a factor or region of thet-haplotype located close to the locus oftf. Althought⁶has a high male segregation ratio, mutants derived from it may have low or normal ratios. In trans heterozygotes of two mutant haplotypes the ratios tended to be equalized, whereas in cis heterozygotes a high ratio liket⁶was obtained, at least in one case. On this evidence the low-ratio geneLowis reinterpreted as a mutantt-haplotype and designatedt^low. It is suggested that abnormal ratio is due to anA-factor or region located between the loci ofTandtf, so thatt⁶carries T-, A- and LS-factors which can exist separately and retain their properties.t⁶may extend less proximally than other naturalt-haplotypes, which in general may involve changes in interstitial heterochromatin.