A Guide to the Russian Academy of Sciences - University of Texas ...

crossing-over in regions proximal to realized chiasma is more
strictly suppressed than in regions located distally.
Chiasma frequency was also studied in mice selected for high body weight
and fertility. Significant effect of the selection on mean chiasma
frequency and its variance was detected. Since recently we have
been studying chromosome pairing in single and double
heterozygotes for two partially overlapping paracentric inversions in
Chromosome 1 of the house mouse In(1)1Rk and In(1)12Rk using
electron microscopy of synaptonemal complexes. We have shown
that the pairing pattern (frequency of homo-, hetero- and asynaptic
configurations) in the inversion heterozygotes depended on the size
and location of the inverted region rather than on its G-band
composition. We found that different regions of the heteromorphic
bivalent are interdependent in their pairing: synapsis in one region
can interfere or facilitate synapsis in another region.
We carried out an examination of the chiasma distribution in chromosome 1
of male mice homozygous and heterozygous for a distal inversion
In(1)12Rk and in karyotypically normal males. A significant
decrease of chiasmata in the subtelomeric region and redistribution
of chiasma frequency in the proximal non-inverted region of the
bivalent 1 were found in heterozygotes. No differences were found
in chiasma distribution between homozygotes for the inversion and
homozygotes for the normal chromosome 1. These results
demonstrate that the frequency of chiasmata depends on a position of
the chromosomal region: a change of localization of the
chromosomal region results in change in chiasma frequency in it. In
the double heterozygotes for inversions we revealed a positive
chromatid interference between exchanges in both inversions. There
is a significant excess of four-chromatid and three-chromatid double
exchanges in comparison with two-chromatid exchanges.
Indications for the positional control of chiasma distribution and for
chromatid interference we consider as the most interesting results of
our study.
Recently we are involved in the different projects concerning the biology of
germ cells in farm animals. We described the sequence of changes in
chromosome behaviour and nuclear morphology during meiotic
prophase in male goats and female pigs, analyzed meiotic
configurations in newly found Robertsonian translocation in cattle
and in interspecific hybrids CattleXBanteng.
We are also taking part in gene mapping in human and the common shrew.
Sector of Immunogenetics of Pig.
7. Meiosis Laboratory
Telephone: 7+3832-35-12-51
Fax: 7+3832-35-65-58
Chromosome pairing and recombination in structural heterozygotes
Gene mapping in the common shrew (Sorex araneus)
Standard karyotype of the house musk shrew (Suncus murinus)
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