TOr1 is a novel, variant form of mouse chromosome 17 with a deletion in a partial t haplotype.

Moutier discovered, in a mouse from a noninbred Swiss/Orleans laboratory stock, a spontaneous dominant mutation which mapped to the T locus, and which was named TOr1. Genetic analyses indicated that TOr1 was not a simple mutation at one locus, but rather a deletion over a 3-centimorgan region of chromosome 17 that included both T and quaking (qk). Further experiments reported by Erickson et al., and a more comprehensive study by Hammerberg, have demonstrated that TOr1 is associated with recessive genetic properties affecting sperm function, characteristic of the proximal region of complete t haplotypes. These results were interpreted as evidence for the location of proximal t haplotype 'sperm factors' within the region deleted by TOr1. We now provide conclusive biochemical and genetic evidence that the 'TOr1 haplotype' is inseparably associated with a chromosomal region derived from a naturally occurring mouse t haplotype. Hence, it is likely that the t haplotype properties of TOr1 are a consequence not of the deletion itself, but of closely linked mutant t haplotype genes.