The origin of a Robertsonian chromosomal translocation in house mice inferred from linked microsatellite markers

The western European house mouse, Mus domesticus, includes many distinct Ro bertsonian (Rb) chromosomal races. Two competing hypotheses may explain the distribution of Rb translocations found in different populations: they may have arisen independently multiple times, or they may have arisen once and been spread through long-distance dispersal. We investigated the origin of the Rb 5.15 translocation using six microsatellite loci linked to the cent romeres of chromosomes 5 and 15 in 84 individuals from three Rb populations and four neighboring standard-karyotype populations. Microsatellite variat ion on the 5.15 metacentric chromosomes was significantly reduced relative to the amount of variation found on acrocentric chromosomes 5 and 15, sugge sting that linked microsatellite loci can track specific mutational events. Phylogenetic analyses resulted in trees which are consistent with multiple origins of the 5.15 metacentric chromosomes found in the three Rb populati ons. These results suggest that cytologically indistinguishable mutations h ave arisen independently in natural populations of house mice.