Search

We calculated the found and expected frequencies of metacentrics in polymorphic populations of the Dnieper basin common rodent, resulting from hybridization of local populations with acrocentric karyotype and four chromosomal races (Neroosa, Kiev, Białowieża, and Western Dvina) with 3–5 diagnostic metacentrics in each. We have previously shown an increased frequency of acrocentric karyotype compared to that expected according to Hardy–Weinberg. The low frequency (less than 0.5) of most metacentrics of the four chromosomal races and the disappearance of some of them from the populations can be explained by the increased fitness of the acrocentric karyotype and the absence of meiotic drive. On the contrary, the preservation of high frequency (more than 0.5) of such metacentrics as gm, hk (races of Western Dvina), hi (races of Kiev), hn, ik (races of Białowieża), and, especially, the fixation of metacentric hi (races of Neroosa) in polymorphic populations can be explained by meiotic drive. The fixation of Rb compounds in the range of the common rodent may be a consequence not only of gene drift but also of meiotic drive. Most likely, meiotic drive is able to maintain the frequency of Rb compounds with the largest acrocentrics g, h, and i, which contributed to the widespread distribution of such compounds throughout the range of the common rodent. [ABSTRACT FROM AUTHOR]

The karyotypes of 95 specimens (57 males and 38 females) of yellow-necked field mouse (Sylvaemus flavicollis Melchior, 1834) caught at seven points in Eastern Europe were studied. Only one specimen had an extra chromosome. It was shown that, in Sylvaemus flavicollis in the surveyed sites from the central part of the range (Eastern Europe), the frequency of occurrence of specimens with B chromosomes is very low and probably does not depend on the ecological conditions of habitats. [ABSTRACT FROM AUTHOR]

A model of the channelized evolution of the S. araneus L. karyotype in the processes of replacement of ten pairs of acrocentric chromosomes by five pairs of metacentric chromosomes has been proposed. The channelized evolution of the karyotype arises due to the inability of Rb-fusions with incomplete (monobrachial) homology to spread in the same population. Therefore, an Rb-fusion, due to some random event first appearing in a population, largely determines the further evolution of the karyotype of that population. After the third replacement of acrocentric chromosomes by metacentric chromosomes, the replacement of the remaining 6 pairs of acrocentrics allows the formation of no more than three karyotypes with five diagnostic metacentrics, which can be predicted, regardless of which rearrangements result in metacentric chromosomes (Rb-fusion or WART). The channelized karyotypic evolution greatly increases the likelihood of parallel karyotype formation, in cases where evolution begins with identical metacentrics in geographically distant populations. An example of parallel evolution that began with the gk metacentric is the identical karyotypes of the new Mogilev race from Belarus and the Tomsk race from Western Siberia. The evolution of Eastern European chromosomal races shows hybrid fusion processes between the karyotypes of the East European karyotypic group (EEKG) and the West European karyotypic group (WEKG). [ABSTRACT FROM AUTHOR]

For 35 years, from 1984 to 2019, in the southern Baikal region, observations of changes in the system of additional chromosomes of Korean field mouse (Apodemus peninsulae) were conducted in five regions. The number and structure of morphotypes of additional chromosomes remained statistically constant. Analysis of B chromosome systems demonstrates stability and low variability of statistical indicators over a 35-year period, as well as the lack of statistical differences between samples of different years. [ABSTRACT FROM AUTHOR]

New data on the karyological variability of Apodemus peninsulae mice (Thomas, 1906) in the Tyva Republic are presented. By the ratio of macro and micro B chromosomes in the mice we studied earlier in this region and in the present study, it became possible to isolate several geographical populations that combine a number of studied catch points of East Asian mice within the territory of the Yenisei River basin in the northern and southern directions from Kyzyl (Republic of Tyva). The frequency distribution of micro B chromosomes makes the most significant contribution to obtaining a differentiation pattern of populations of mice with B chromosomes by area. [ABSTRACT FROM AUTHOR]