[Sequences homologous to mouse mammary cancer virus are common in mammalian and avian genomes].

Sequences distantly related to mouse mammary tumor virus (MRS) were found in a wide range of mammalian genomes using blot hybridization. The number of MRS copies and the degree of their relationship with the hybridization probe varied and did not correlate with the evolutionary similarity of the species. Nevertheless, within a genus the set of MRS was species-specific and reflected the degree of relationship between species. MRS were also found in avian genomes and the degree of their relationship also did not correlate with the evolutionary similarity of the species. The origin and distribution of MRS are discussed.