ISSN 10227954, Russian Journal of Genetics, 2012, Vol. 48, No. 10, pp. 1020–1028. © Pleiades Publishing, Inc., 2012.
Original Russian Text © Yu.M. Borisov, B.I. Sheftel, L.D. Safronova, D.Yu. Aleksandrov, 2012, published in Genetika, 2012, Vol. 48, No. 10, pp. 1190–1199.
The EastAsian (Korean) mouse
Thomas, 1906 has a constant
Achromosome set, which consists of 48 acrocentric
chromosomes, and B chromosomes, which substan
tially vary in number (from 1 to 30) and occur in the
majority of individuals [1–11]. Five Bchromosome
classes are recognized by size and morphology: large,
medium, small with two arms, small acrocentric, and
micro B chromosomes [2–6]. The Bchromosome
classes form specific combinations, which differ in
morphotype number and proportion, in almost each
individual mouse from Siberian populations .
The natural Bchromosome variants were found to
act as an integral and differentiating character of Sibe
rian geographical populations of
In general, the population variants observed for the
Bchromosome system over the large species area may
display a minor cyclic variation in individual years, but
remain stable over prolonged periods of time . A
longterm exposure to mutagenic factors (including
technogenic ones) distorts the homeostatic processes
in populations, changing the Bchromosome number
and morphotypes in
. The variation of
the Bchromosome system was observed in an Altai
Mountain population for many years, and a new
microevolutionary phenomenon was discovered: a
threefold increase in the Bchromosome number over
22 years (from 1980 to 2002) [7, 8]. The mean number
of B chromosomes in
increased from 2.3
in 1980 to 6.5 in 2002. Examinations of mice from the
same population were carried out in 2006 and 2008
and showed that the mean Bchromosome number
stabilized at a new higher level, 6.5 and 7.1, respec
tively [8, 10].
The Bchromosome population systems remained
stable in other
populations from other
localities of the vast species range, as demonstrated in
studies of various years [1–9].
In 1980s, we started a population genetic study of
the variants of the Bchromosome system in
from Northern Mongolia as a region that was lest
affected by technogenic factors in recent years . The
study was continued in 2007 and 2010.
MATERIALS AND METHODS
We analyzed the new data on the variants of the
Bchromosome system in 22
which were captured in 2007 and 2010 in taiga of West
ern Hentei (in the vicinity of the HoninNuga biolog
ical station, 150 km north of UlanBator, Mongolia).
In addition, we examined the karyotype of one
female, which was captured 250 km north of
the town of Chita (Buryatia, Bautovskii raion, Vitim
Plateau, village of Bagdarin, the valley of the Badgarin
River) by I.V. Moroldoev (table).
The variation of the Bchromosome system was
compared for this and neighbor
tions from Northern Mongolia, the Baikal region, and
Transbaikalia on the basis of the data reported previ
ously [4–6]. Published data [12–14] were also
included in the analysis.
Mice were collected in the vicinity of the Honin
Nuga biological station in 2007 and 2010. In total, we
captured and examined 10 mice 2007, when the
mouse population size was low (1.9 mice per 100 cyl
inder–days), and 12 mice in 2010, when the popula
tion size was high (54.7 mice per 100 cylinder–days).
Chromosome preparations were obtained using bone
Stability of the Population Variants of the BChromosome System
in the EastAsian Mouse
from the Baikal
Region and Northern Mongolia
Yu. M. Borisov, B. I. Sheftel, L. D. Safronova, and D. Yu. Aleksandrov
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 119071 Russia;
Received May 18, 2011
—Analysis of the Bchromosome frequency and morphotypes in 160 mice
from 17 localities of the Baikal region, Northern Mongolia, TransBaikalia, and the Russian Far East showed
that the mice were from five geographical populations. The interpopulation difference was determined by
variations of 0–4 macro B chromosomes and 0–11 micro B chromosomes. The Bchromosome number and
morphotypes proved to be stable over the past 30 years in the geographical populations under study.