Successive waves of fixation of B1 variants in rodent lineage history.

A new method of analyzing phylogenetic relations among members of sequence family (Quentin 1988) discriminates at least six possible B1 subfamilies in the mouse genome. Several additional and independent observations suggest that these groupings have evolutionary significance, and that successive waves of fixation of new variants occur during rodent lineage history. We have reason to believe that, in a genome, the founder sequences of different families of retroposons are in competition with regard to the amplification/fixation process.