Spontaneour Robertsonian fusion leading to karyotype variation in the house mouse - first report form Asia

Evolution of the structure and composition of house mouse satellite DNA sequences in the subgenus Mus (Rodentia: Muridea): a cytogenomic approach

The composition and orientation of the house mouse satellite DNA sequences (minor, major, TLC) were investigated by a FISH and CO-FISH approach in 11 taxa belonging to three clades of the subgenus Mus. Using a phylogenetic framework, our results highlighted two distribution patterns. The TLC satellite, the most recently discovered satellite, was present in all clades but varied quantitatively among species. This distribution supported its appearance in the ancestor of the subgenus followed by independent evolution in species of each clade. In contrast, the minor and major satellites occurred in only two clades of the subgenus indicating the simultaneous and recent amplification of these sequences. In addition, although qualitative differences in the composition and orientation of the satellite sequences were observed among the taxa, none of the features studied were unique to the house mouse and could account for the extensive chromosomal plasticity evidenced in Mus musculus domesticus.

Implications of the genetic divergence between European wild mice with Robertsonian translocations from the viewpoint of mitochondrial DNA

Genetic divergences between the wild mouse populations with various Robertsonian translocations from the Poschiavo Valley, Yugoslavia, Milan and the Apenninies, were estimated based on the mitochondrial (mt) DNAs. The mtDNAs isolated from the liver were analysed by agarose slab-gel electrophoresis after digestion with eight kinds of restriction endonucleases: BamHI, EcoRI, HindII, HindIII, PstI, HpaI, HpaII and BgII. These preparations were further used to make restriction maps, from which sequence divergence between each Rb variation was calculated to be 0·2–2·2%. These rather larger values appear to be in conflict with the present concept that the Rb variations occurred during the last several thousand years. Both, however, might be reconciled by assuming genetic introgression of the founder with a small number of Rb translocations into other subspecies populations genetically remote and the subsequent rapid accumulation of Rb translocations unique to each population due to an unknown mechanism occurring specifically in the intersubspecies hybrids betweenM. m. domesticusand the otherM. m. subspecies. This was the case also in a new Rb (9.15) translocation obtained from Ogasawara Islands in Japan which was the intersubspecies hybrid betweenM. m. molossinusandM. m. domesticus.

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.

Stable and transmissible dicentric chromosome with terminal centromeres in ascites cell of mouse sarcoma 180

The occurrence of a stable and transmissible dicentric chromosome with 2 terminal centromers has been reported in the ascites form of mouse sarcoma 180 cells which is chromosomally hypotetraploid. The number of such dicentrics is 2 in all endoreduplicated cells. The probable mode of anaphase separation of the dicentric has been discussed.

Robertsonian fusion leading to the formation of stable dicentric chromosome in an ascites cell line of the mouse

The dicentric nature of a marker metacentric chromosome originated by robertsonian fusion has been established in the ascites cells of mouse sarcoma 180. C-banding analysis has revealed that the metacentric is actually a dicentric with 2 closely situated C-positive heterochromatic zones. The nature of the centromeres and the NF value of the cell indicate that this meta-dicentric marker has originated by breakage and fusion within each of the short arms of 2 acrocentric chromosomes.