EVIDENCE FOR MULTIPLE FUNCTIONAL COPIES OF THE MOLE SEX-DETERMINING LOCUS, SRY, IN AFRICAN MURINE RODENTS

Southern hybridization data suggest that the male sex-determining locu s, Sry, is often duplicated in rodents. Here we explore DNA sequence e volution of orthologous and paralogous copies of Sry isolated from six species of African murines. PCR amplification followed by direct sequ encing revealed from two to four copies of Sry per species. All copies include a long open reading frame, with a stop codon that coincides c losely with the stop codon of the house mouse, Mus musculus, a species known to have a single copy of Sr?: A phylogenetic analysis suggests that there are at least seven paralogous copies of Sry in this group o f rodents. Putative orthologues are identical; sequence divergence amo ng putative paralogues ranges from 1 to 8% (excluding the CAG repeat), with much lower levels of divergence in the high-mobility group (HMG- box) region than in the C-terminal region. A high proportion of nucleo tide substitutions in both regions result in aminoacid replacement. Th e long open reading frame, conserved HMG-box, and pattern of evolution of the putative paralogues suggest that they are functional.