Complex medico-genetic study of the Western Siberian population. II. Population-genetic study of fluorescent chromosome polymorphism in Northern Khanty

Polymorphisms of fluorescent variants of 469 human karyotypes from five subpopulations of the Northern Khanty were studied. Significant frequency variability of Q-polymorphic variants of chromosomes was shown. Wahlund's variance for 12 chromosome polymorphic segments was 0.0121, while the total inbreeding coefficient was 0.0069 with a negative nonrandom component. Heterozygosity estimated for chromosome fluorescent polymorphism (0.189) agrees well with that for blood group systems and less for enzymes. The frequencies of Q-polymorphic variants corresponded to Hardy-Weinberg equilibrium, except for chromosome 13 which gave the significant excess of heterozygotes. Possible explanations of this phenomenon are discussed.     

Q- and C-band polymorphism of the chromosomes in a group of patients with the Shereshevski?-Turner syndrome

Q- and C-band polymorphism of heterochromatic regions of chromosomes were studied in a group of patients with Turner's syndrome (30 girls with the karyotype 45, X) and in 105 normal individuals. No significant differences in the frequencies of Q-polymorphic variants for the most part of chromosomes studied (with the exception of chromosome 13 satellites) were obtained between patients with Turner's syndrome and the control. There were no differences in the mean number of Q-variants per individual in both groups investigated. An increase in the frequency of large C-segments of chromosome 9 was detected in patients with Turner's syndrome. An increase in the frequency of individuals carrying a combination of several extreme variants in the individual karyotype was found for patients with Turner's syndrome. The differences revealed are of non-specific character for a given form of developmental pathology.     

Human chromosomal polymorphism. III. Chromosomal Q polymorphism in Mongoloids of northern Asia

Summary Q-heterochromatin variants in seven autosomes (3, 4, 13–15, 21, 22) were studied in two Mongoloid populations of northern Asia (Chukchi and Khakass). Q-staining was obtained using propylquinacrine mustard. Of 132 Chukchi individuals aged 13 to 20 years, 124 had Q-polymorphic chromosomes, while eight (6.0%) had no bands with fluorescence levels 4 and 5. The mean number of Q variants was 2.2 per individual.Of the 120 Khakass individuals aged 14 to 17 years, 112 had Q-polymorphic chromosomes, while eight (6.7%) had no Q variants with fluorescence levels 4 and 5. The mean number of Q variants was 2.5 per individual. No differences were found in the frequency of Q variants between sexes in the two populations. There was complete agreement between the observed homo-and heteromorphic frequencies and those predicted by the law of Hardy-Weinberg. As the Mongoloid populations of northern Asia showed statistically significant homogeneity both in the frequency of Q variants and the distribution of homo-and heteromorphic variants, they were examined as a single group—that of northern Mongoloids. The following questions are discussed: (1) the possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to certain extreme environmental factors, in particular to cold and hypoxia; (2) the intraracial heterogeneity of Asian Mongoloids; (3) the taxonomic value of chromosomal Q polymorphism in ethnic anthropology.     

Human chromosome variation: the discriminatory power of Q-band heteromorphism (variant) analysis in distinguishing between individuals, with specific application to cases of questionable paternity.

The chromosomes from 57 persons were analyzed by means of quinacrine fluorescent staining in order to assess the amount of variation and the discriminatory power of Q-band heteromorphism analysis. Chromosomes 3, 4, 13, 14, 15, 21, 22, and Y of each person were visually compared to those of 56 others, for a total of 1,596 comparisons. No two persons were found to have the same set of variants. The number of differences between chromosomes for each comparison ranged from 2 to 12 out of a possible total of 14 for females and 15 for males. Relatives were also distinguishable, and differences ranged from two to seven. We used the frequency with which each chromosome was useful for telling two people apart, and estimated the probability of finding two persons with the same set of quinacrine variants as .0003. Distinctly different heteromorphisms were found in the 39 unrelated persons for each of the chromosomes examined. In this small population, the number of different sets of variants observed for chromosomes 3, 4, 13, 14, 15, 21, 22, and Y were six, seven, 27, 16, 20, 15, 24, and five, respectively, for a total number of possible combinations of 1.14 X 10(15). As a test of the usefulness of chromosome heteromorphisms in paternity cases, 12 father-mother-child trios of virtually certain paternity, owing to the father-child segregation of a rare structural rearrangement, were coded and recombined at random to produce 120 cases of uncertain paternity. When the code was broken, 108 "alleged fathers" had been excluded correctly and the 12 biological fathers had been included correctly.     

Human chromosomal polymorphism. I. Chromosomal Q polymorphism in Mongoloid populations of central Asia

Summary A comparative study of frequencies and types of Q-polymorphic variants in seven autosome pairs (3, 4, 13–15, 21, and 22) was performed in three steppe Mongoloid populations of Central Asia (Kazakhs, Dunghans, Mongolians) and three highland Kirghiz populations of Pamir and Tien-Shan. The three steppe Mongoloid populations showed statistically significant homogeneity both in the frequency of Q-polymorphic variants and the distribution of homo- and heteromorphs, with complete agreement of observed frequencies with those theoretically predicted by the law of Hardy-Weinberg. Similar homogeneity was revealed in the three highland Kirghiz populations of Pamir and Tien-Shan. However, comparative analysis of highland and steppe Mongoloids revealed significant differences in the following variables: (1) mean number of Q variants per individual, 2.50 and 3.49 in the highland and steppe populations, respectively; (2) frequency of Q variants in 7 of the 12 autosomes studied; and (3) distribution of homo- and heteromorphs in four autosomal pairs (13–15, 21) with a preponderance of individuals with increased homomorph (-/-) frequency in highlanders.The following questions are discussed: (1) the possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to extreme environmental factors, in particular to the high-altitude environment of Pamir and Tien-Shan; (2) the existence of intraracial heterogeneity in Mongoloids living in different ecological zones; and (3) the possible taxonomic value of Q-variant inversion in chromosome 3.     

Human chromosomal polymorphism

Chromosomal Q-polymorphism was studied in 198 Kirghiz subjects (98 males and 100 females) from one high-altitude isolate located in the south-eastern part of Kirghizia. Small samples of mountaineers (N = 37) and volunteer subjects (N = 34) were also studied. The samples studied did not differ significantly from each other in the relative frequencies of chromosomal variants in 12 loci of seven Q-polymorphic autosomes. The mean number of Q variants per individual in the populations ranged from 1.3 to 2.0. No sex differences were found in the frequencies of Q variants. The observed homo- and heteromorphic frequencies agreed with those predicted by the law of Hardy-Weinberg. The possible selective value of chromosomal Q heterochromatin material in the adaptation of human populations to high-altitude climate is discussed.     

Evolutionary strata on the X chromosomes of the dioecious plant Silene latifolia: evidence from new sex-linked genes

Despite its recent evolutionary origin, the sex chromosome system of the plant Silene latifolia shows signs of progressive suppression of recombination having created evolutionary strata of different X-Y divergence on sex chromosomes. However, even after 8 years of effort, this result is based on analyses of five sex-linked gene sequences, and the maximum divergence (and thus the age of this plant's sex chromosome system) has remained uncertain. More genes are therefore needed. Here, by segregation analysis of intron size variants (ISVS) and single nucleotide polymorphisms (SNPs), we identify three new Y-linked genes, one being duplicated on the Y chromosome, and test for evolutionary strata. All the new genes have homologs on the X and Y chromosomes. Synonymous divergence estimated between the X and Y homolog pairs is within the range of those already reported. Genetic mapping of the new X-linked loci shows that the map is the same in all three families that have been studied so far and that X-Y divergence increases with genetic distance from the pseudoautosomal region. We can now conclude that the divergence value is saturated, confirming the cessation of X-Y recombination in the evolution of the sex chromosomes at approximately 10-20 MYA.     

The DNA-based human karyotype

Image cytometry and computer analysis are used to determine the relative DNA content and the DNA-based centromeric index of the 24 chromosomes of the human karyotype. A two-step procedure is used. Chromosomes of cells in metaphase first are stained with quinacrine and identified visually by their fluorescent Q-band patterns. They then are stained for DNA using gallocyanin-chrome alum. The chromosome images are scanned and recorded as digital values of optical density by an CYDAC image cytometric microscope system, CYDAC. The digital images are processed by computer to measure for each chromosome the relative DNA stain contents of the whole chromosome and of the p and q arms and the DNA-based centromeric index. About ten cells are analyzed for each of the donors, who are phenotypically normal men and women. The chromosome measurements are pooled by chromosome type for each donor and are compared among donors. The means of the chromosome measurements give the DNA-based human karyotype. Analysis of the DNA-based data shows that some chromosomes or portions of chromosomes vary significantly among donors. These variants do not correlate with detectable morphologic polymorphisms, such as Q- or C-band variants; thus they represent new and otherwise undetectable chromosome polymorphisms whose genetic basis and clinical significance are yet to be determined.     

Interaction among different heterocromatic variants in the grasshopper Dichroplus elongatus

Simultaneous chromosome polymorphisms for supernumerary elements allow us to analyse the relationships among different forms of heterochromatic variation in nature. We report simultaneous variation patterns for supernumerary segments in chromosomes S10 (SS10), S9 (SS9) and S6 (SS6) and B chromosomes in nine populations of the grasshopper Dichroplus elongatus from two biogeographic provinces from east Argentina. Our results show spatial chromosome differentiation for three out of four supernumerary heterochromatic variants (B chromosomes, SS6 and SS10). The incidence of B chromosomes was negatively correlated with the SS10 frequency. The distribution pattern analysis shows different degree of differentiation among populations for each supernumerary heterochromatic variant suggesting that the detected chromosome variation cannot be explained by interaction between migration and genetic drift. Moreover, the observed population chromosome differentiation was not in agreement with the hierarchical analysis of molecular of heterogeneity at mitochondrial DNA level (mtDNA). The present results point out the importance of the interaction among heterochromatic variants in the chromosome intraspecific variation in east Argentina natural populations of the grasshopper D. elongatus.     

Linkage studies of polymorphic, repeated DNA sequences in centromeric regions of human chromosomes.

The DNA at human centromeric regions was characterized by using a repetitive sequence, 308, which localizes in situ exclusively to centromeres of all chromosomes. We previously noted that this sequence is enriched on chromosome 6 and has chromosome-specific organization on 6, 3, 7, 14, X, and Y. In addition to this basic organization, sequences homologous to 308 are polymorphic among normal individuals. The variants are transmitted in a Mendelian manner within a family. To determine the chromosome origin of the variants, we studied their linkage to markers of various chromosomes. Linkage analysis of one pedigree segregating two polymorphisms shows that the 2.6-kilobase (kb) BamHI and 2.6-kb TaqI fragments are linked to each other and to the HLA loci on chromosome 6. Data from another family shows that 2.8-kb TaqI, 4.0-kb TaqI, and 1.3-kb BamHI polymorphic fragments are linked and are probably near the Fy locus on chromosome 1. By dot blot analysis, we determined that the relative amount of these sequences in the genome is not measurably different between unrelated individuals. Thus, the polymorphisms represent changes in homologous 308 sequences on specific chromosomes and can be used as chromosome-specific markers. Linkage studies using polymorphisms of repeated sequences will be most useful within a kindred, especially from an inbred population, because polymorphic repeats of the same restriction size may be heterogeneous in origin.     

Inter- and intraplant C-banding polymorphism in one population ofAegilops comosa subsp.comosa var.comosa (Poaceae)

The Giemsa C-banding pattern of the chromosomes of the native self-pollinatedAegilops comosa subsp.comosa var.comosa was studied. Six of the seven chromosomes of the haploid genome were found to be polymorphic for C-banding patterns. Chromosome A had four variants, chromosome E three variants and each of the chromosomes B, D, and F two variants. Chromosomes E and G were polymorphic for arm length and arm ratio.This paper is part of the doctoral dissertation ofA. Georgiou.     

Evidence for degeneration of the Y chromosome in the dioecious plant Silene latifolia

The human Y--probably because of its nonrecombining nature--has lost 97% of its genes since X and Y chromosomes started to diverge [1, 2]. There are clear signs of degeneration in the Drosophila miranda neoY chromosome (an autosome fused to the Y chromosome), with neoY genes showing faster protein evolution [3-6], accumulation of unpreferred codons [6], more insertions of transposable elements [5, 7], and lower levels of expression [8] than neoX genes. In the many other taxa with sex chromosomes, Y degeneration has hardly been studied. In plants, many genes are expressed in pollen [9], and strong pollen selection may oppose the degeneration of plant Y chromosomes [10]. Silene latifolia is a dioecious plant with young heteromorphic sex chromosomes [11, 12]. Here we test whether the S. latifolia Y chromosome is undergoing genetic degeneration by analyzing seven sex-linked genes. S. latifolia Y-linked genes tend to evolve faster at the protein level than their X-linked homologs, and they have lower expression levels. Several Y gene introns have increased in length, with evidence for transposable-element accumulation. We detect signs of degeneration in most of the Y-linked gene sequences analyzed, similar to those of animal Y-linked and neo-Y chromosome genes.     

Determination of the DNA content of human chromosomes by flow cytometry

The mean relative DNA content of each human chromosome was calculated from flow karyotypes of ethidium bromide-stained chromosomes obtained from healthy, normal individuals. These values were found to correlate closely with previously published data obtained by photometric scanning of stained, fixed chromosomes. Calculations of the normal variation in DNA content of each human chromosome indicated that chromosomes 1, 9, 16, and Y (chromosomes with large centric heterochromatic regions) were the most variable, followed by the acrocentrics, 13, 14, 15, 21, and 22. Chromosomes 2, 3, 18, and 19 were also found to vary significantly in DNA content. Chromosomes from a number of subjects with extreme heteromorphisms were flow karyotyped to obtain an estimate of the extent of variation in DNA content of each chromosome. The greatest difference between extreme variants was found for chromosome 1 (which differed by 0.82% of the total genomic DNA), followed by 16 and 9. The largest Y-chromosome variant was 85.9% bigger than the smallest. The precise karyotype analysis produced by flow cytometry resolved many differences between chromosome homologs, including some that cannot be readily distinguished cytogenetically. The implications of these findings for detection of chromosome abnormalities by flow karyotype analysis are discussed.     

Human acrocentric chromosomal associations in old age

Associations of satellite chromosome fibres of acrocentric chromosomes of the DD, GG and DG types were studied in persons aged from 80 to 114 years. It was found that the value of P (probability of joining of satellite fibres of two chromosomes in a group) is considerably less than the corresponding value for persons aged from 20 to 48 years. It is supposed that the decrease of the frequency of association at senile age is caused by heterochromatization of satellite fibres in the 13th and 14 chromosome pairs.     

Co-occurrences of polymorphic heterochromatin regions of chromosomes and effect on reproductive failure

Although the polymorphic heterochromatin regions of chromosomes (heteromorphisms) have been extensively studied for their phenotypic effects on humans, co-occurrences of chromosome 1, 9, 16 and Y heteromorphisms and of acrocentric variants have never been studied on humans with an objective scoring system. Here we compared the frequencies of individual heteromorphisms on a total of 602, 768 and 224 patients with the indications of infertility, recurrent miscarriage and in vitro fertilization (IVF) failure, respectively and on 272 controls. Then we examined whether there were significant co-occurrences between heteromorphisms within and between the groups. There were no statistically significant differences in the frequencies of heteromorphisms between the groups. Both statistically significant and non-significant correlations were observed within the non-acrocentric and certain acrocentric heteromorphisms in each group. When these co-occurrences were examined between the groups, a 2.2 fold increased risk of IVF failure in males in the presence of either chromosome 13 or chromosome 21 variants was observed (95 %CI:1.1–4.2). We conclude that the simultaneous manifestations of heteromorphisms have no effect on reproductive failure. There seems to be a correlation between the non-acrocentric heteromorphisms (1qh+, 9qh+, 16qh + and Yqh+/-), which might be the result of complex interactions of formation of these heterochromatin regions. The correlations observed between certain acrocentric chromosomes might be related to satellite association and nucleolus formation. The increased risk observed in males with IVF failure in the presence of either chromosome 13 or 21 variants should be interpreted cautiously due to the heterogeneity of the group.     

Widespread Recombination Suppression Facilitates Plant Sex Chromosome Evolution

Classical models suggest that recombination rates on sex chromosomes evolve in a stepwise manner to localize sexually antagonistic variants in the sex in which they are beneficial, thereby lowering rates of recombination between X and Y chromosomes. However, it is also possible that sex chromosome formation occurs in regions with preexisting recombination suppression. To evaluate these possibilities, we constructed linkage maps and a chromosome-scale genome assembly for the dioecious plant Rumex hastatulus. This species has a polymorphic karyotype with a young neo-sex chromosome, resulting from a Robertsonian fusion between the X chromosome and an autosome, in part of its geographic range. We identified the shared and neo-sex chromosomes using comparative genetic maps of the two cytotypes. We found that sex-linked regions of both the ancestral and the neo-sex chromosomes are embedded in large regions of low recombination. Furthermore, our comparison of the recombination landscape of the neo-sex chromosome to its autosomal homolog indicates that low recombination rates mainly preceded sex linkage. These patterns are not unique to the sex chromosomes; all chromosomes were characterized by massive regions of suppressed recombination spanning most of each chromosome. This represents an extreme case of the periphery-biased recombination seen in other systems with large chromosomes. Across all chromosomes, gene and repetitive sequence density correlated with recombination rate, with patterns of variation differing by repetitive element type. Our findings suggest that ancestrally low rates of recombination may facilitate the formation and subsequent evolution of heteromorphic sex chromosomes.     

臭鼩染色体的研究

本文采用骨髓染色体制片法,对捕自我国浙江萧山市的臭鼩进行了组型、G-带、C-带和核仁组织区银染的观察分析。结果表明,我国臭鼩染色体数目为2n=40,组型为8(m)+2(sm)+10(st)+18(t),性染色体为,(?):X(m或sm),Y(m或sm);♀:XX(m或sm)。G-带较为丰富,每一对染色体都有其特定的带型,较易于辨别与配对。在C-带方前,4对中间着丝粒染色体与5对亚端着丝粒染色体均具有不同程度的着丝粒带,1对亚中着丝粒染色体与9对端着丝粒染色体缺乏C-带物质,性染色体具丰富的远端带及中间带.银染的结果显示,第5、12和13对染色体具银染物质。     

Chromosomal variation and zoogeography inAteles

Karyotypes are reported from 21 spider monkeys distributed among five taxa of the genus Ateles.G- and C- banding techniques revealed variations between taxa. Two variants were discovered for chromosome 5, for chromosome 7, and for the Y chromosome. Four forms of chromosome 6 were seen. The variations are all probably pericentric inversions. One individual was heteromorphic at position 6. The data are compared with prebanding reports of Ateleschromosomes and reports of five animals studied with banding techniques. The variation in Ateleschromosomes is similar in degree to that found in other ceboid genera. The variants may be related to forest refugia formed during the Plio-Pleistocene. Karyotyping of many New World primates is required to ensure a homogeneous experimental group.     

Chromosome distribution studies after inorganic lead exposure

Summary We studied the chromosome distribution in persons professionally exposed to inorganic lead. The degree of lead exposure was evaluated by biochemical measurements and cytogenetic analysis. The chromosome distribution was analyzed from trypsin banded karyotypes; in particular we studied centromere distances ² and centromere-metaphase-center distances (d²) which were obtained by computer-aided mathematical transformation of the individual metaphase coordinates.Higher concentrations of blood lead and urine -ALA and a statistically significant increase in aneuploidy, hypoploidy, and type-B chromosome aberrations revealed appreciable exposure although none of the subjects showed signs of excessive lead absorption.However study of the chromosome distribution showed no major differences with that of the controls indicating that lead acts preferentially (directly or indirectly) on the chromosomes rather than on the spindle apparatus. A dissociation of the acrocentric chromosomes was observed in the lead group when compared with the controls. This is thought to reflect a secondary action of lead on the nucleolar organiser regions.     

Karyological characteristics of cell sublines of the kidney of the kangaroo rat and of skin fibroblasts of the Indian muntjac

A study was made of the karyotypic structure of sublines derived from the kangaroo rat's kidney (NBL-3) and skin fibroblasts of the Indian muntjac, available in the cell culture bank of the Institute of Cytology Acad. Sci. USSR. A comparative karyologic analysis was made of subline NBL-3 both contaminated with mycoplasma (NBLK) and decontaminated with antibiotics (NBLD). Authentic differences in cell distribution according to chromosome number in NBLK and NBLD variants were shown. Modal numbers of chromosomes are 11 and 17, respectively. The modal number for the Indian muntjac cell subline (MT) is 9. 60-80% of the cells had an identical karyotype (the main structural variant of the karyotype is MSVK). Using the G-banding technique, all the MSVK variants were shown to display constant karyotypes. In NBLK there are 5 pairs of homologous chromosomes and one metacentric. In NBLD, the number of homologous chromosomes increased in all the groups (hypotriploid karyotype). In subline MT 3 homologous chromosomes were found in groups I and IV, 2 in group III in addition to one X-chromosome. A comparison with the Indian muntjac karyotype showed the absence of marker chromosomes in MT. The analysis of additional SVK shows that the deviations from MSVK are caused mostly by changes in the number of homologous chromosomes within the groups. A study of the frequency of deviations in chromosome numbers observed in the groups from MSVK showed that different chromosomes were involved in karyotypic changes in the same way in the "low-chromosome" variants of NBLK and MT, and in different ways in NBLD. A comparison of the "premycoplasmic" variants of line NBL-3 with NBLK shows no differences in the parameters studied.(ABSTRACT TRUNCATED AT 250 WORDS)