Zoogeography of the chromosome 1 HSR in natural populations of the house mouse (Mus musculus).

A polymorphism of the central part of chromosome 1 has been described from natural populations of the house mouse (Mus musculus). The region shows up as a C band-positive homogeneously staining region (HSR) under the light microscope. M. m. domesticus mice carry single band HSRs, whereas M. m. musculus animals have double band HSRs. HSR size variations have been described in both subspecies. The frequency of the HSR chromosome 1 in populations varies from 4% to 81%, but none of the large samples examined consisted only of homozygotes. In the subspecies M. m. domesticus, HSRs were found in North Africa and Western Europe, mainly in the hilly regions of Southern Germany and Switzerland. Localities with double HSRs are distributed all over the area of M. m. musculus. Based on the population data presented and DNA similarity of different HSRs, the origin and distribution of HSR chromosomes in the house mouse are discussed.