Genetic transmission of mammary tumour virus in the DBAf mouse strain.

MTV antigens were demonstrable by radioimmunoassay in milk samples from individual DBAf mice, and in samples from (male BALB/c X female DBAf) F1 mice. Although some samples collected during the first lactation periods of these mice were virus-negative, all samples of later lactation periods were virus-positive. From 75 mice of the [ male BALB/c X female (male BALB/c X female DBAf)]Bc I population, milk samples were collected during one or more lactation periods and tested for the presence of viral antigens; the samples of 42 mice were virus-positive. In the ([BALB/c X (BALB/c X DBAf)] X BALB/c)Bc II population two groups were distinguished. In the first group, the progeny of virus-positive Bc I mothers, 37 out of 62 mice had detectable levels of viral antigen in the milk. None of the 43 samples from mice of the second group, derived from MTV-negative Bc I females, were virus-positive. These data suggest that the presence of viral antigens in the milk of DBAf mice is controlled by a single dominant gene; evidence for linkage of this gene and the albino locus was obtained (recombination percentage: 20).