Genetic variation of wild mouse populations in southern Germany: I. Cytogenetic study

Some 400 wild mice (Mus domesticus) from southern Germany (the triangle formed by the cities Tübingen, Heidenheim and Friedrichshafen) were karyotyped and, in 243 of them, the chromosome compositions were determined by banding techniques. Virtually all mice tested carried at least one pair of metacentric chromosomes; some mice had up to ten metacentric chromosomes. Based on their chromosome composition, five mouse populations could be distinguished. Population I was characterized by the diploid chromosome number of 2n = 38 and the presence of two copies of metacentric chromosome Rb(4.12)1Tu. This translocation was also found in virtually all mice captured in southern Germany, almost always in a homozygous state. Mice of other populations had extra metacentric chromosomes Rb(5.15)15Tu (population II), Rb(13.14)17Tu (population III), Rb(5.14)18Tu (population IV) and Rb(11.13)6Tu (population V). In addition, rare variants (1 or 2 mice) were found in the different populations, which were heterozygous for additional metacentric chromosomes. Population V was quite heterogeneous in that it contained up to five metacentric chromosomes in addition to those mentioned. The number and the composition of these metacentric chromosomes varied from place to place. With the exception of population I, the individual populations occupied geographically distinct areas: Representatives of population I were found concentrated in one area, but, in addition, some were scattered over the entire studied region.