Alleles at a Mutable Locus Found in Populations of Wild House Mice ( Mus Musculus )

Abstract

In attempting to determine the rate of mutability at the T locus (short tails) among wild populations of mice, a high frequency of +/tn heterozygotes (tn interacts with T to give tailless) was found. A study was made to determine the frequency and nature of the tn alleles by mating wild mice from different sources with T/+ offspring from 2 inbred Brachy lines and crossing the offspring with known balanced lethal lines. Tests of 12 males from New York population samples indicated that 7 were +/tw and 5 +/+ Crosses among Fi T/tw mice indicated that the wild sample had at least 2 different tw alleles, one lethal and one viable, and resembling the t-alleles from laboratory populations. The wild males +/tw produced an excess of tw sperm in the ratio of about 8 tw 1 +. When the tw1 and tw2 alleles were combined with tO and t1 alleles from laboratory populations, the males of all combns. tested were mating sterile although occasional sperm may be functional. A single male from a second New York population was designated [plus or minus]/tw5 after testing. Two out of 3 samples from Wisconsin populations had no apparent tn alleles, but contained minus modifiers of Brachy which made them unsuitable for the detection of tn alleles. A tw allele was found in the 3d sample which may be the same as t0 in the laboratory strains. One out of 3 wild females from Connecticut had tw3, but no tw alleles were found in 4 wild males from Vermont and 5 wild males from Maine. In addition to heterogeneity at the T locus samples from wild populations also showed variation in belly color and in white spotting.