Biomedical subjects

I P Gorlov

Publications and source records attributed to I P Gorlov.

32 records · Page 2Linked to original sources

PubMed1990

Synapsis in single and double heterozygotes for partially overlapping inversions in chromosome 1 of the house mouse.

Electron microscopic (EM) analysis of synaptonemal complexes (SC) in single and double heterozygotes for the partially overlapping inversions In(1)1Icg, In(1)1Rk and In(1)12Rk in chromosome 1 of the house mouse reveals that synapsis and synaptic adjustment are dependent on the size and location of the inversions and interaction between the latter. Is(1)1Icg contains insertions of the inverted repeats Is(HSR;1C5)1Icg and Is(HSR;1D)2Icg and an inverted euchromatic region. Synaptic adjustment of the D-loops by shortening of the asynapsed segments of the lateral elements belonging to the insertions occurs at the late zytogene to early pachytene stage. Synaptic adjustment of the inversion loops takes place at early to late pachytene. A delay in adjustment was found in the double heterozygotes In(1)1Icg/In(1)1Rk and In(1)1Icg/In(1)12Rk. A correspondence between the lifespan of asynapsis in inverted regions and the probability of association of XY and heteromorphic bivalents was revealed.

Animals↗

PubMed1990

The origin of a double insertion of homogeneously staining regions in the house mouse (Mus musculus musculus).

A high resolution analysis of the G-band patterns of normal and aberrant chromosomes 1, bearing two linked insertions of homogeneously staining regions (HSRs) in the house mouse (Mus musculus musculus) reveals the inverted pattern of the euchromatic region between the HSRs. On the basis of this analysis a hypothesis on the origin of the aberrant chromosome is put forward: the double insertion is a result of an inversion of the chromosome 1 of Mus musculus domesticus bearing a single insertion of HSR. The proximal breakpoint is localized inside the HSR, and the distal one between subbands E3 and E4.

Animals↗

PubMed1990

[The causes of appearance of a double insertion of homogeneously staining regions in the chromosome 1 of house mouse (Mus musculus musculus)].

A high resolution analysis of G-band pattern of normal and aberrant chromosome 1 bearing two linked insertions of homogeneously staining regions (HSRs) in the house mouse (Mus musculus musculus) reveals an inverted pattern of the euchromatic region between the HSRs. On the basis of this analysis, a hypothesis on the causes for appearance of the aberrant chromosome was put forward: the double insertion is a result of inversion of the chromosome 1 of Mus musculus domesticus bearing a single long insertion. The proximal breakpoint is localized inside the HSR and the distal one--between subbands E3 and E4. From the point of view of these data, new symbols for the aberrations are proposed: Ls (HSR, 1C5) 1Icg--for the proximal insertion, Is(HSR, 1D)21cg--for the distal one, In (1) 1Icg--for the inverted region, including the bands D, E1-E3 and the insertion Is(HSR 1D)21cg.

Animals↗

PubMed1990

[Synapsis and recombination of chromosomes in the house mouse homozygous for the double inversion of the homogeneously stained regions in chromosome 1].

Examination of the meiotic pattern of chromosome 1 isolated from feral mouse population and containing a double insertion (Is) of homogeneously staining regions (HSRs) was carried out. In the previous study it has been shown that the region delineated by the proximal break point of Is(HSR; 1C5) 1Icg and the distal one of Is(HSR; 1E3) 2Icg is desynapsed during early pachytene and heterosynapsed at midpachytene. No synaptic disturbances were revealed in homozygotes in this study. Chiasma frequency in hetero- (1.87) and in homozygous (1.88) males was shown to be higher than in normal ones (1.61). Thus, insertion of recombinationally inert heterochromatic regions leads to increase in the length of genetic map of the chromosome via physical elongation and relaxation of interferential restrictions.

Animals↗

PubMed1990

[Cytogenetic study of synapsis and crossing-over in male mice heterozygous for reciprocal translocation T(14; 15)6Ca].

Synapsis and crossing over in male mice heterozygous for reciprocal translocation T (14; 15)6Ca were studied. The translocated multivalent undergoes the synaptic adjustment in the course of meiotic prophase. Translocated distal region of the 14th chromosome forms inproportionally long lateral element of synaptonemal complex. The number of chiasmata in the 14th chromosome increases from 1.02 0.02 in normal karyotype to 1.41 0.03 in heterozygous mice. The density of chiasmata in translocated, distal region is ten times higher than in the other part of the 14th chromosome.

Animals↗

PubMed1990

[Synapsis in single and double heterozygotes for partially overlapping inversions in chromosome 1 of the house mouse].

Electron microscopic analysis of synaptonemal complexes (SC) in single and double heterozygotes for the partially overlapping inversions In(1)1Icg, In(1)1Rk and In(1)12Rk in the Chromosome 1 of the house mouse reveals a dependence of synapsis and synaptic adjustment on the size and location of the inversions and their interaction. In(1)1Icg contains the insertions of inverted repeats Is(HSR: 1C5)1Icg and Is(HSR: 1I)2Icg as well as inverted euchromatic region. The synaptic adjustment of the D loops by shortening of asynapsed parts of the lateral elements of SC belonging to the insertions occurs at late zygotene-early pachytene stage. After that the synaptic adjustment of the inversion loops takes place. A delay in adjustment was found in diheterozygotes In(1)1Icg/In(1)1Rk and In(1)1Icg/In(1)12Rk. Morphological alterations of the asynapted terminal segments of lateral elements preventing synaptic adjustment were found in single and double heterozygotes for In(1)1Rk and In(1)12Rk. Correspondence between the size of asynapted regions and the probability of association of XY and heteromorphic bivalents was revealed.

Animals↗

PubMed1989

[Effect of heterozygosity for insertions of homogeneously stained regions in chromosome 1 of the house mouse on synapsis in meiotic prophase].

Electron microscope analysis of surface-spread synaptonemal complexes (SC) in oocytes and spermatocytes from double cis heterozygotes for Is(HSR; 1C5)1Icg and Is(HSR; 1E3)2Icg was carried out. Aberrant chromosomes were isolated from the feral population of Mus musculus musculus of Novosibirsk. They contain homogeneously stained regions of total length of about 30% of Chr 1 mitotic metaphase. Heteromorphic bivalents of Chr1 with different lengths of the lateral elements of SC and the loop in the intermedial position were revealed in 4.4% spermatocytes and 20% oocytes of heterozygous animals. The loop size depends on the stage of meiosis: it is maximal at late zygotene and decreases up to disappearance during pachytene.

Animals↗

PubMed1989

[Effect of double insertion of homogeneously stained regions in chromosome 1 of the house mouse on recombination frequency].

By means of genetic and cytogenetic analysis, the effect of cis heterozygosity for two insertions--Is(HSR; 1C5)1Icg and Is (HSR; 1E3)2Icg was studied. It was shown that the proximal point of Is is situated 8 cM distally from the ln gene. Crossing over is completely suppressed in the intermedial part of Chr. 1, where a single chiasma appears in normal mice. The frequency of double chiasmata in heterozygotes is significantly increased. They are localized at precentromeric and pretelomeric parts of Chr. 1. It is supposed that recombination block in the central region leads to a shift of the potential chiasmata in telomeric regions. This shifted telomeric chiasmata, in turn, allow the appearance of the second chiasmata in the centromeric region.

Animals↗

PubMed1988

[A new variant of chromosome 1 in the house mouse].

In wild mouse populations of Siberia, animals with a new variant of chromosome 1 were found. The total length of this chromosome was 1.3 times as great as the normal homologue. The G-banding technique revealed two additional insertions Is(HSR; 1C5)1Icg and Is(HSR; 1E3)2Icg located between bands 1C5 and 1D, and 1E3 and 1E4, resp. The C-banding of both the insertions was positive and lighter than that of the centromeric heterochromatin. The size of each insertion was approximately 15% of new variant of chromosome 1. No meiotic disturbances were found in heterozygous male mice. Chromosome 1 with insertions has been introduced into the laboratory mouse stock.

Animals↗

PubMed1988

[Distribution of chiasmas in the 2d and 6th chromosomes involved in Robertsonian translocations in male mice].

The distribution of chiasmata in 2 and 6 chromosomes in males homozygous for Rb(2.6)4Iem and Rb(8.17)1Iem was studied. Chiasmata were shown to distribute along chromosomes non-randomly, exchanges occurring in telomeric regions. Chiasmata distribution is substantially different for the cases of one and two chiasmata per bivalent. The main cause for these differences is supposed to be strong positive chiasmata interference (the position of the first chiasma may determine the position of the second one). The centromere blocks this effect, so chiasma in one arm does not interfere with that in the second arm. It has been shown that the frequency of double exchanges depended on not only the distance between markers under study, but also on marker position in the chromosome.

Animals↗

PubMed1987

[Localization of genes on mouse chromosomes by comparing the genetic map and chiasma distribution].

It is possible to determine chromosomal position of the genes having definite genetic localization, using chiasmata distribution along the chromosome. This approach was used for subchromosomal mapping of the house mouse genes. It was shown that the chiasmata distributions are different for different chromosomes. The positions of some gene on chromosomes 1, 2, 17 and 19 were determined. The results coincide with those on subchromosomal gene mapping using chromosome translocations and in situ hybridization.

Animals↗

PubMed1986

[Cytogenetic consequences of hybridization between wild and laboratory mice].

Wild mice from the aboriginal population were crossed with the laboratory C57BL/6 mice. F1 hybrids were backcrossed with both parents. Significant increase of recombination frequency in the AY-Ra region of the 2nd chromosome (from 22.0 to 33.1 cM), of the frequency of occurrence of X-Y univalents (up to 54.6%) and of autosomal univalents (up to 9.1%) was found in the F1. In backcrosses all these induces decreased gradually.

Animals↗

PubMed1986

[Effect of emotional stress on the frequency of meiotic abnormalities in male mice].

The effect of stress on the recombination frequencies at the 1st and 2nd chromosomes of male mice was shown earlier. The purpose of this work is the study of the stress effects on the behaviour of meiotic chromosomes. Male mice (A/He and DD/J inbred strains) were treated with acute immobilizing stress at different periods, prior to killing. It was shown that the stress significantly increases the frequency of X-Y and autosomal univalents in metaphase 1 and aneuploidy in metaphase 2. The most sensitive to the stress are the late interphase - early leptotene cells.

11-Hydroxycorticosteroids↗

PubMedDate not supplied

Double insertion of homogeneously staining regions in chromosome 1 of wild Mus musculus musculus: effects on chromosome pairing and recombination.

An examination of the meiotic pattern of chromosome 1 isolated from a feral mouse population and containing a double insertion (Is) of homogeneously staining regions (HSRs) was carried out. The region delineated by the proximal breakpoint of Is(HSR;1C5) 1Icg and the distal breakpoint of Is(HSR;1E3)2Icg is desynapsed during the early pachytene stage and heterosynapsed at the midpachytene, as shown by electron microscopic analysis of synaptonemal complexes. The HSRs have no effect on the segregation of chromosome 1 in heterozygous mice. The lack of homosynapsis in the region under study causes chiasmata redistribution in heteromorphic bivalents. In normal males, single chiasmata are located in the medial part of the chromosome. In heterozygotes, this segment is heterosynapsed and unavailable for recombination. This leads to a significant decrease in the frequency of bivalents bearing single chiasmata. The total number of chiasmata per bivalent is much higher in heterozygous males than in normal ones. The recombination frequency between proximal markers fz and In also is higher in heterozygous animals. The increase in the total chiasma number in the heteromorphic bivalent is due to the addition of double chiasmata located mostly at precentromeric and pretelomeric regions of the chromosome.

Animals↗