Transmission of mammary tumor virus in mouse strain DD: further support for the uniqueness of strain GR.

Outcrosses between high tumor mouse strain DD and low-incidence strains BALB/c and C57BL to produce reciprocal F1 susceptible offspring of both types resulted in high incidences of mammary tumors in (DD female X BALB/c male)F1 and (DD female X C57BL male)F1 females but not in the reciprocal hybrids with DD as the male parent. The finding that transmission of murine mammary tumor virus (MuMTV) in DD was through the milk, as most often observed in mouse strains, further supported the uniqueness of strain GR in which MuMTV is transmitted by either parent.