Polymorphism of human chromosomes 1, 9, 16, Y: Variations,segregation and mosaicism

Summary A study was carried out on C-banded chromosomes 1, 9, 16, Y from an unselected population and from 30 normal families. We found: a) great variability in length and position of the C-bands; b) somatic mosaicism involving C-bands; c) variants in children that were not present in parental patterns. The possible role of crossing-over in generating the last two phenomena is 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

Summary Comparative analysis of the polymorphism of C segments on chromosomes 1, 9, 16, and Y was conducted in 50 normal boys and 50 normal girls. Quantitative methods revealed that the mean lengths of C segments, their variability, and their distribution on the chromosomes mentioned are quite identical in the two groups. Methodological problems related to the study of chromosome polymorphism are discussed.     

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.     

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.     

Distamycin A/DAPI bands and the effects of 5-azacytidine on the chromosomes of the chimpanzee, Pan troglodytes

The chromosomes of the chimpanzee were stained with distamycin A/DAPI, which labels specific C-bands. Bright distamycin A/DAPI fluorescence was found in the heterochromatic regions of chromosomes 6, 11, 14 to 16, 18 to 20, and 23 and the Y. Lymphocyte cultures from chimpanzees were treated with low doses of 5-azacytidine during the last hours of culture. This cytosine analog induces highly distinct undercondensations in 28 heterochromatic regions of 19 chromosomes. These 5-azacytidine-sensitive regions are predominantly located in the terminal C-bands of the chromosomes. In vitro treatment with 5-azacytidine also preserves into the metaphase stage somatic pairings between the 5-azacytidine-sensitive heterochromatic regions in interphase nuclei. The homologies and differences regarding the chromosomal localization of distamycin A/DAPI-bright C-bands, 5-azacytidine-sensitive heterochromatin, 5-methylcytosine-rich DNA sequences, and satellite DNAs in the chimpanzee and man are discussed.     

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.     

C-heterochromatin and extra (B) chromosome distribution in six species of the Nabis (Heteroptera, Nabidae) with the modal male karyotype 2n = 16 + XY

The basic male karyotype of the six Nabis species (Heteroptera, Nabidae) is confirmed as being 2n=16+XY. The chromosomes are holokinetic while male meiosis is achiasmatic. The sex chromosomes undergo postreduction and in second metaphase show distance pairing, registered in all nabid species examined so far. Using C-banding technique for the first time in the family Nabidae, the heterochromatin was revealed on chromosomes of six species. The species showed different amount and distribution of C-heterochromatin. Only in Nabis (Dolichonabis) limbatus did the C-bands distribution make possible the identification of every chromosome pair in the karyotype. In other species, C-bands were found in some of the autosomes and the X, localized either interstitially or at telomeres. Only the Y usually showed relative stability ofthe C-banding pattern. In four of six species, extra (B) chromosomes were observed and their behaviour in meiosis described.     

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.     

C-polymorphism of chromosomes in men with azoospermia

Comparative evaluation of absolute C-segment lengths of chromosomes 1, 9, 16 and Y in 50 azoospermic males has revealed significant differences in chromosome 9 between 50 normal males. These results are considered as nonrandom in pathology of male gametogenesis.     

Characterization of human chromosomal constitutive heterochromatin

The constitutive heterochromatin of human chromosomes is evaluated by various selective staining techniques, i.e., CBG, G-11, distamycin A plus 4,6-diamidino-2-phenylindole-2-HCl (DA/DAPI), the fluorochrome D287/170, and Giemsa staining following the treatments with restriction endonucleases AluI and HaeIII. It is suggested that the constitutive heterochromatin could be arbitrarily divided into at least seven types depending on the staining profiles expressed by different regions of C-bands. The pericentromeric C-bands of chromosomes 1, 5, 7, 9, 13-18, and 20-22 consist of more than one type of chromatin, of which chromosome 1 presents the highest degree of heterogeneity. Chromosomes 3 and 4 show relatively less consistent heterogeneous fractions in their C-bands. The C-bands of chromosomes 10, 19, and the Y do not have much heterogeneity but have characteristic patterns with other methods using restriction endonucleases. Chromosomes 2, 6, 8, 11, 12, and X have homogeneous bands stained by the CBG technique only. Among the chromosomes with smaller pericentric C-bands, chromosome 18 shows frequent heteromorphic variants for the size and position (inversions) of the AluI resistant fraction of C-band. The analysis of various types of heterochromatin with respect to specific satellite and nonsatellite DNA sequences suggest that the staining profiles are probably related to sequence diversity.     

C-bands in chromosomes 1,9, and 16 of twins

Summary Thirty-two pairs of Caucasoid twins, 16 monozygotic (MZ) and 16 dizygotic (DZ) of the same sex, were studied in relation to the C-bands of chromosomes 1, 9, and 16. Concordance was not absolute among MZ, the best evaluation of the degree of genetic determination for these traits being 0.40 for chromosome 16, 0.64 for chromosome 1, and 0.73 for chromosome 9. Possible explanations for the failure to obtain 100% concordance are methodologic shortcomings, intercell variations in chromosome contraction, and unequal mitotic crossing over.     

Counterstained enhancement of TaqI resistant sites after distamycin A/diamidinophenylindole treatment

Numerous selective and differential staining techniques have been used to investigate the hierarchical organisation of the human genome. This investigation demonstrates the unique characteristics that are produced on fixed human chromosomes when sequential procedures involving restriction endonuclease TaqI, distamycin A (DA) and 4,6-diamidino-2-phenylindole (DAPI) are employed. TaqI produces extensive gaps in the heterochromatic regions associated with satellite II and III DNAs of human chromosomes 1, 9, 15, 16 and Y. DA/DAPI selectively highlights, as brightly fluorescent C-bands, the heterochromatin associated with the alpha, beta, satellite II and III DNAs of these chromosomes. When DA and DAPI are used on chromosomes before TaqI digestion, and then stained with Giemsa, the centromeric regions appear to be more resistant, producing a distinct C-banding pattern and gaps in the heterochromatin regions. Sequential use of the DA/DAPI technique after TaqI treatment produces a bright fluorescence on the remaining pericentromeric regions of chromosomes 1, 9, 16 and Y, which also displayed a cytochemically unique banding pattern. This approach has produced specific enhanced chromosomal bands, which may serve as tools to characterize genomic heterochromatin at a fundamental level.     

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.     

Patterns of chromosome banding in four nabid species (Heteroptera, Cimicomorpha, Nabidae) with high chromosome number karyotypes

Male Nabis (Aspilaspis) indicus (St?l), N. (A.) viridulus Spinola, Himacerus (Himacerus) mirmicoides (O. Costa) (2n=32+XY) and Prostemma guttula (Fabricius) (2n=26+XY) were studied using C-banding, silver nitrate staining and base-specific fluorochrome (DAPI and CMA(3)) staining. N. indicus differed from N. viridulus in distribution pattern of C-bands, which were telomeric in the former while interstitial in the latter. H. mirmicoides showed interstitial C-bands in the majority of autosomes. P. guttula had no conspicuous C-bands in other chromosomes, but only in the Y, which was totally heterochromatic. C-heterochromatin was labelled with DAPI, indicating that it was AT-rich. In every species, both X and Y chromosomes were NOR-bearing, and the NOR regions were GC-rich. In H.mirmicoides and P. guttula, NORs showed sub-median location in the X and distal in the Y, such a pattern being probably common in Nabidae. The present paper provides new information on the genome organization and new cytological markers useful for a better insight into karyotype evolution of nabid species.     

Variability and familial transmission of constitutive heterochromatin of human chromosomes evaluated by the method of linear measurement

Summary Using the method of linear measurement, the lengths of constitutive heterochromatin of chromosomes 1, 9, 16, and Y were determined in 125 unrelated individuals, and in 30 members of ten families. The method used eliminates the variations in the C-band length due to different degrees of contraction of chromosomes in different mitoses, and enables the size of heterochromatin blocks to be expressed. It was found that the distribution of C-band lengths in the group of 125 individuals was normal, i.e., Gaussian, for all four classes of chromosomes measured. On the basis of length distribution and by computing the P₁, P₁₀, P₉₀ and P₉₉ percentiles, the actual numerical limits could be proposed for the five-step evaluation of heterochromatin length according to the Paris Conference (1971), Supplement (1975), for chromosomes 1, 9, 16, and in a preliminary way also for Y. When applying the proposed limits to data obtained in the present study, 165 C-band variants could be identified among the 125 individuals.In ten families, C-block lengths of the chromosomes transmitted from parents to progeny could be determined in 63 cases. The mean difference in C-band length of transmitted chromosomes, as measured in parents and in children, was 0.46×10^-7 m. An analysis was carried out to detect the factors upon which the magnitude of this difference depends, and to define what differences are attributable to methodological errors. The results revealed that the difference rises slightly with the increasing length of the measured C block. Three degrees, defined by concrete ranges of difference in C-block length, were proposed for expressing the probability that the compared chromosomes had been transmitted.The study further attests to the effectiveness of the method of constitutive heterochromatin measurement for paternity testing. In our set of ten families, the comparison of C-band lengths of chromosomes 1, 9, 16, and Y led to rejection of paternity in 64% of unrelated individuals; excluding the Y chromosome, the percentage decreased to 61. As many as 47% of the individuals were rejected by a difference higher than two units (i.e., transmission of the compared chromosome highly improbable).     

Restrictive localization of centromeric heterochromatin (C-bands) in Presbytis e. entellus (Dufresne) as compared to Macaca mulatta (Zimmerman)

C-bands are observed in the centromeric regions of only three pairs of autosomes and the distal portion of the small acrocentric Y in a total complement of 44 chromosomes of a male Presbytis e. entellus. Simultaneously treated slides of a Rhesus monkey, however, have C-bands in all the 42 chromosomes. The lack of C-bands may be due to (1) absence of highly repetitive DNA in the centromeric region of certain chromosomes or (2) presence of minute quantity of such DNA which is imperceptible or (3) different types of centromeric heterochromatin with a varying degree of repetition of DNA sequences all of which do not react in similar manner to various techniques employed at present. It is hypothesized that the centromeric heterochromatin rich in satellite DNA helps in withstanding the force of excessive coiling of chromosomes at the centromere to facilitate the functioning of the genes for microtubular protein during cell division when other genes are rendered inactive due to compactness of chromosomes.     

Equivalence of the total constitutive heterochromatin content by an interchromosomal compensation in the C band sizes of chromosomes 1, 9, 16, and Y in Caucasian and Japanese individuals

A quantitative analysis of C bands by densitometric measurements in chromosomes 1, 9, 16, and Y was conducted in Caucasians and Japanese living in Brazil. Sixty normal unrelated subjects (30 males and 30 females) were studied in each racial group. Caucasians presented C bands of chromosomes 1, 9, and 16 larger than Japanese, but, on average, only the difference for C bands of chromosome 9 was statistically significant. In the Japanese, the C band sizes of chromosomes Y were, on average, significantly larger than in the Caucasians. The mean C band size of chromosome 9 and the sum of the three pairs were significantly larger in Caucasian than in Japanese males. The total values of constitutive heterochromatin, sigma (1qh,9qh,16qh,Yq12), did not show significant difference between Caucasian and Japanese males. The relative C band sizes of chromosomes 1, 9, and 16 were, on average, similar in Caucasians and Japanese. No sex difference was found in both racial groups. As regards the heteromorphism, only the values of C bands of chromosome 9 were, on average, significantly larger in Caucasians than in Japanese. Partial inversions were detected only among the Caucasians.     

The staining of constitutive heterochromatin,and A-T and G-C rich DNA in lymphocytes and primary spermatocytes of the Chinese hamster

The staining of male Chinese hamster chromosomes at meiotic prophase with several banding techniques is described. C-banding results only occasionally in well-differentiated pachytene and diakinesis bivalents. Meiotic C-bands are small compared with those in somatic metaphase chromosomes. In mice C-bands mainly consist of highly repetitive satellite DNA, whereas in Chinese hamsters the majority of the DNA in C-bands is not or hardly repetitive. Especially in Chinese hamsters both the degree of chromatin despiralisation and the folding pattern of the chromatin drastically reduce the distinction of C-bands in late meiotic prophasc chromosomes. In contrast to the situation in mice, C-heterochromatin associations are never observed in Chinese hamster spermatocytes. It is assumed that the presence of satellite DNA rather than constitutive heterochromatin is the basis for the associations of the paracentromeric chromosome regions in mice. The location and behaviour of AT- and GC-rich DNA in Chinese hamster primary spermatocytes is studied with base-specific fluorochromes (H 33258 and Chromomycin A₃ for AT-and GC-rich DNA respectively), in combination with a pretreatment with base-specific non-fluorescent antibiotics (Actinomycin D and Netropsin for GC-and AT-rich DNA respectively). No indications are found for the clustering of AT-or GC-rich DNA in Chinese hamster pachytene nuclei. A comparison of banding patterns observed in somatic metaphases and in diakinesis gives some information about the partial homology of the X and Y chromosome. The results are conflicting. The short arm of the Y chromosome is homologous with a part of the X chromosome. According to the C-band pattern the long arm of the X chromosome is involved in the pairing with Y, whereas fluorescence banding patterns indicate that it is the short arm of X.     

A simple method to sequentially reveal Q- and C-bands on the same metaphase chromosomes

The Q-C staining procedure, i.e., to treat QM stained preparations with a modified ASG method, conveniently provides Q? and C? (instead of the expected G?) bands on the same metaphase chromosomes. This procedure is especially useful for karyological study of heteroploid cells and interspecific cell hybrids in which extensive chromosomal rearrangements and complex karyotypic compositions are present. A few examples of karyological interest are reported. C-bands, which are either Q+ or Q?, can be divided into two to three subsegments in human chromosomes 1, 9, and 16. These subsegments are connected by a Q?/C?element. Interstitial C-bands could have originated mostly from a C-band without the kinetochore or with the“non-functional” kinetochore.“Double Minutes” are of two kinds, Q+/C+ and Q?/C+. Mechanism for the production of C-bands by the Q-C procedure is briefly discussed.