ROSLIK G.V., KARTAVTSEVA I.V., PAVLENKO M.V., BAZHENOV YU.A.
Genetika 2026; 62(5): 48-63
Mosaicism in the number of B chromosomes was studied in Apodemus peninsulae karyotypes from the Zabaikalsky Krai. A high frequency of mosaics was found, particularly in samples from the “southeastern” group II (91%) on the right banks of the Shilka and Onon rivers. Mosaics comprised between 2 and 6 cellular clones, with animals having 2, 3 and 4 cellular clones being predominant. For the first time, the mitotic instability index (MI) was analyzed in the Korean field mouse. Approximately 70% of the animals exhibited high MI values, as along with negative accumulation index (A) values. These quantitative parameters of mosaicism indicate mitotic instability of B chromosomes and a predominance of their elimination over accumulation. It is shown that the frequency characteristics of mosaicism—along with quantitative and morphotypic parameters of Bs—can serve as an additional trait for differentiating the «northwestern» and «southeastern» geographic groups of samples. The boundary between these groups runs along the Shilka and Onon rivers. The adaptive significance of mosaicism in A. peninsulae populations is discussed.
