Heterochromatic regions of human chromosomes 1, 9, 16 and Y and the phenotype

The relationship between variability of the heterochromatic regions of chromosomes 1, 9, 16, Y and the anthropometric characteristics (the height, the biacromial diameter and weight) was studied in two groups of children; 70 children had embryopathies of unknown etiology and 40 children had the Down syndrome. The positive statistically significant correlation of the C-segments lengths of chromosomes 1, 9, 16, their sum included, and above characteristics was found. The correlation coefficients of Y-chromosome were non-significant. The problems of functional role of the structural heterochromatin and its influence on viability and physical development of the organism are discussed.     

The quantitative analysis of polymorphism on human chromosomes 1, 9, 16 and Y

Summary The generalized characteristic of the C-segment lengths on chromosomes 1, 9, 16, and Y is suggested for a study of population heterogeneity. For this purpose, the concept of the distance D is introduced, taking into account the individual C-segment lengths, the mean lengths and standard deviations of C-segment lengths in a group of subjects, as well as the coefficients of correlation of the C-segment lengths on the said chromosomes.It is demonstrated that distance D may be employed to study the relevance of the given subject to the group studied, the relation to the mean characteristics within the group, and selection of subjects' pairs with almost identical C-segment lengths on respective chromosomes.In the study of such problems as zygosity of twins, family analysis, etc., along with the absolute C-segment lengths, it is recommended to employ the relative C-segment lengths on chromosomes 1, 9, 16, and Y, calculated as a part of the sum total of their absolute lengths.     

The quantitative analysis of polymorphism on human chromosomes 1, 9, 16, and Y

This study was made to establish a stable quantitative characteristic of C segments on chromosomes 1, 9, 16, and Y in an individual karyotype that was reproducible in successive experiments. The C segment of these chromosomes were measured in successive cultures of cells from three males and the C segments of chromosomes 1, 9, and 16 in cells from three pairs of female monozygotic twins were measured. The results show that the absolute lengths of C segments tend to vary considerably with the cell samples analyzed, while the relative length, i.e., the length of a single C segment as a percentage of the total length of all C segments of the chromosomes being studied, is more stable and can be used for individual characteristics.     

The quantitative analysis of polymorphism on human chromosomes 1, 9, 16, and Y

Summary A paracentric inversion of chromosome 5 was detected after RHG banding in a subject affected by Klinefelter's syndrome. The inversion was also observed in the patient's mother, and was confirmed by QFQ-and RBA-banding techniques.A second paracentric inversion affecting chromosome 7 was detected in a woman with Turner's syndrome. The same structural anomaly was found in her father and her half-brother.The possible relationship between sex chromosome nondisjunction and paracentric inversion is discussed.Furthermore, the inversion of chromosome 7 reproduces exactly the chromosome 7 of the gorilla, which is presumed to be ancestral to the human 7. This therefore appears to be the first reported case of reverse chromosomal mutation.     

The segregation of C-band polymorphisms on chromosomes 1, 9, and 16.

Eleven normal families with at least four children were studied cytogenetically using the C-band technique to identify polymorphisms in the constitutive heterochromatin of chromosomes 1, 9 and 16. Thirteen individuals showed one or more variants in such chromosomes. The analysis of the segregation ratios in the 35 offspring of these 13 individuals showed that these marker chromosomes generally segregated according to the expected 50:50. However, one of these variants, chromosome no. 9 with an increased heterochromatin block in the secondary constriction, has an apparently preferential segregation, when the findings from this study are combined with those of other authors.     

Analysis of the inheritance of heterochromatic regions in human chromosomes 1, 9, 16 and Y

The inheritance of heterochromatic regions of chromosomes 1, 9, 16 and Y was studied in twelve families by means of measuring their C-segments. Maternal and paternal origin of chromosomes 1, 9 and 16 in the child was determined by two methods. The advantages and disadvantages of these methods and possibilities of their application are under discussion.     

Mitomycin C induced structural changes in heterochromatic regions of human chromosomes 1, 9, 16 and Y

Aberrations and variations in the heterochromatic blocks of chromosomes 1, 9, 16 and Y were found under the influence of mitomycin C in cultured lymphocytes of peripheral human blood. Lymphocytes were cultured during 96 hours, mitomycin C in final concentration of 0.3 mkg/ml was present in the culture during the latest 24 hours of culturing. Different changes in the heterochromatic regions of chromosomes were found in approximately 30% of cells: in 6.3% of cells mitotic chiasmata were indicated. In 9.5% of cells isolocus breaks were observed in heterochromatic region of chromosome 1 in segment 1q11. In the latter case this may be a fragile site detected under the influence of mitomycin C on the lymphocytes.     

C-polymorphism of chromosomes 1, 9, 16 and Y in newborn infants of various gestational ages

Comparative evaluation of absolute C-segment lengths of chromosomes 1, 9, 16 and Y in new-born children of different gestational age has revealed no significant differences in their value between individuals with unfinished intrauterine development and those born in time.     

Differential condensation of human chromosomes 9 and Y

Some differences were observed in the mitotic condensation of regions composing human chromosomes 9 and Y: regions 9p, 9h and Y nf are characterized by an intense condensation by the end of the spiralization interval studied (the length of the repair chromosome 3 varying from 5.4 to 2.9 mkm). At the same time, the condensation of regions 9q-h (region 9q without heterochromatic block) is slowing in the initial spiralization interval (the length of chromosome 3 varying from 16.6 to 5.5 mkm). The Yf-block of Y-chromosome is condensing faster than nf-region. The condensation parameters of Q-heterochromatic blocks are most variable while the euchromatic regions are most stable. The dynamics of 9h and of f-block condensation are independent within one karyotype. Based on the data obtained we doubt the correctness of studies on linear dimensions of the constitutive heterochromatin blocks for the evaluation of its quantity in the karyotype. A possible association of differential mitotic condensation with the chromosome segregation disturbances is discussed.     

Quantitative analysis of C-segments of chromosomes 1, 9, 16 and Y in couples with reproductive disorders

A comparative analysis of structural variability of C-bands on chromosomes 1, 9, 16 and Y was conducted in 50 phenotypically normal adults and 25 couples with repeated spontaneous abortions. Reduction of both the total amount of heterochromatin in the cell and the lengths of these regions on chromosomes 1, 9, and 16 is revealed in the group of pathology. No differences were found in the lengths of C-bands on Y chromosome.     

Classification of qh regions in human chromosomes 1, 9, and 16 by C-banding

Summary We present a classification for secondary constriction (qh) regions with C-banding technique in chromosomes 1,9, and 16 by means of comparing them to the short arm of chromosome 16. It is simple and convenient and can be used routinely. It can be incorporated into the modified Paris nomenclature system.     

Quantitative analysis of C bands in chromosomes 1, 9, 16 and Y in Caucasian and Japanese males

A comparative analysis of the C bands of chromosomes 1, 9, 16 and Y of 27 Caucasian and 27 Japanese males is reported. The mean of the total centromeric heterochromatin of the three pairs (sigma h1, 9, 16) is larger in Caucasian than in Japanese subjects, but Caucasians showed a lower mean of C band size of chromosome Y. Heritability of the C band of the Y chromosome was studied in 26 families.     

Polymorphism of heterochromatin regions of chromosomes 1, 9, 16 and Y in long-lived persons and in persons of various ages from 2 areas of the Soviet Union

Variants of the chromosome polymorphism have been studied in long-living individuals and in persons of the population group from the Abkhazian region. This study and a comparative analysis of the data obtained with the data of the analogous studies of 170 persons in the Ukraine have permitted establishing the peculiarities of the distribution of certain chromosome polymorphism variants in long-living individuals.     

Heterochromatic regions on chromosomes 1, 9, 16, and Y in children with some disturbances occurring during embryo development

Some reduction of C-segment lengths and their variability on chromosomes 1, 9, 16, and Y was exhibited by children who had had some disturbances at early stages of morphogenesis. The data obtained might suggest a certain activity of the heterochromatic regions during embryo development. Based on this data one may also suppose that reduction of the amount of heterochromatin might affect the normal morphogenetic processes.     

Analysis of centromere size in human chromosomes 1, 9, 15, and 16 by electron microscopy.

Human chromosomes were treated with 5-azacytidine and analyzed by whole-mount electron microscopy. This base analogue produces undercondensation of heterochromatin and separation of the centromere from the bulk of pericentromeric heterochromatin in chromosomes 1, 9, 15, and 16, which allows clear delimitation of the centromere regions. A quantitative analysis of centromeres showed that chromosomes 1, 9, and 16 have centromeres of different size. The centromere of chromosome 15 is similar in size to that of chromosome 9 and different from those of chromosomes 1 and 16. No interindividual variation for centromere size was found. A positive correlation between centromere and chromosome size was found for the chromosomes analyzed.     

Centromeric instability of chromosomes 1, 9, and 16 associated with combined immunodeficiency

Summary Instability of the centromeric regions of chromosomes 1, 9, and 16 in cultured lymphocytes of an 8-month-old girl with malabsorption and combined immunodeficiency is reported. Together with the two previous reports on this condition, the present report seems to confirm the specific association of combined immunodeficiency and centromeric instability of chromosomes 1, 9 and 16 with multibranching.     

Homoeologic aberrations in human and chimpanzee Y chromosomes: inverted and satellited Y chromosomes

An inverted and a satellited Y chromosome detected in peripheral blood lymphocytes of a chimpanzee and a pygmy chimpanzee, respectively, were characterized cytogenetically by various banding techniques. A detailed comparison with an inverted and a satellited Y chromosome in man suggested that the corresponding aberrations were homoeologic.     

Heterochromatic regions and the nondisjunction of human chromosome 21. I. Polymorphism of the C-bands of chromosomes 1, 9 and 16 in children with Down's syndrome

To test a hypothesis on potential role of large heterochromatic regions in chromosome nondisjunction polymorphism of C segments of chromosomes 1, 9, and 16 in 70 children with Down's syndrome were examined. The C segment lengths of the above chromosomes were shown not to deviate from the normal. To solve the problem, it seems unreasonable to examine children with Down's syndrome.     

Polymorphisms for human chromosomes 1 and Y: Feulgen and UV DNA measurements

Some individuals show considerable length differences between the homologues of chromosome no. 1 and length variations for the Y chromosome have also been found. The variabilities in length appear to be localized in the heterochromatic regions. The aim of this study was to distinguish between two phenomena postulated to contribute to length variations: (1) a genetically determined uncoiling of a chromosomal region, and (2) an increase in the chromosomal DNA content. By cytophotometry of photographic negatives the integrated absorbance of polymorphic and normal no. 1 and Y-chromosomes was compared, using chromosome no. 2 as standard. Microphotometry was carried out on both unstained chromosomes at 265 nm and on Feulgen-stained chromosomes at 546 nm. Both methods showed that the length polymorphisms studied are, in general, characterized by an increase in the chromosomal DNA.     

Patterns of exchange induced by mitomycin C in C-bands of human chromosomes. I. Relationship to C-band size in chromosomes 1, 9, and 16

Summary Frequencies of exchange were determined in C-bands of chromosomes 1, 9 and 16 in six normal males, and related to relative C-band area. Comparing these different chromosomes, more exchanges occurred on average in 9 than in 1 although their mean C-band sizes were similar. Chromosome 16 exchanges were fewer, both overall and relative to C-band area. Comparing the same chromosome between individuals, there was a positive correlation between relative frequency and band size in both 1-1 and 9-9 exchanges. No clear trend was observed for other exchange events.If homology is required for interchange, if cannot be dependent solely on overall C-band size. Perhaps certain DNA sequences, sensitive to mitomycin C damage, are located in part of each C-band, with less per unit area in chromosome 1 than in 9 and still less in chromosome 16.X- and U-type exchanges between chromosome 9s occurred in near equal frequencies in all individuals. If synapsis of specific, affected sequences is a pre-requisite for interchange, this observation suggests that the affected sequence in chromosome 9 is arranged in both orientations relative to the centromere.