An additional type of male sterility and inherited urinary obstruction in mice with the t-haplotype th7.

The t-complex on mouse chromosome 17 results in transmission ratio distortion in males heterozygous for complete haplotypes, and sterility in those homozygous for semi-lethal or doubly heterozygous for complementing lethal haplotypes. This sterility is due to inability of spermatozoa to fertilize. The haplotype th7 is an unusual laboratory-derived haplotype, postulated to carry a small duplication of t chromatin. Males heterozygous for th7 show a new form of sterility, apparently due to failure to form copulation plugs during mating. This is accompanied by a strong propensity to acute urinary obstruction. It is suggested that both the failure to form copulation plugs and the urinary obstruction are due to some abnormality in function of the accessory sex glands, and are the result of incorrect dosage of a gene in the postulated duplication. The symbol Msu for male sterility and urinary obstruction is suggested for the locus concerned. Previously a recessive form of abnormal behaviour had also been attributed to this duplication.