Smaller autosomal C band sizes in Blacks than in Caucasoids.
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Black People↗
Biomedical subjects
M S Mattevi
Publications and source records attributed to M S Mattevi.
Unusual C-band patterns in three karyotypically rearranged forms of Scapteromys (Rodentia, Cricetidae) from Brazil.
Chromosome studies of 30 specimens of the rodent Scapteromys collected at nine localities in southern Brazil revealed the occurrence of three karyotypic taxa with 2n = 36 (one locality), 34 (two localities), and 24 (six localities), although all three had 40 autosomal arms (AN). The G-band analysis indicated that this reduction in diploid number was mainly due to Robertsonian translocations which have occurred along a gradient, possibly in two independent evolutive routes. The C-bands occur on one autosomal pair and on the X and Y in the 2n = 36 and 34 forms and on the X and Y chromosomes only in the 2n = 24 taxon. The broad genomic reorganization which has occurred in this genus, in which the chromosomes do not have large amounts of constitutive heterochromatin, argues against the idea that a large amount of constitutive heterochromatin favors chromosome evolution and speciation.
Animals↗
An X1X1X2X2/X1X2Y mechanism of sex determination in a South American rodent, Deltamys kempi (Rodentia, Cricetidae).
Chromosome studies on 14 specimens of Deltamys kempi disclosed six males with 2n = 37, NF = 38, six females with 2n = 38, NF = 38, and two females with 2n = 37, NF = 38. G- and C-band analyses revealed a Y-autosome translocation in the males leading to a multiple chromosome system of sex determination of the type X1X1X2X2/X1X2Y, this being the second case of such a mechanism described in rodents. At meiosis the males presented a trivalent in which C-banding studies showed an alternate orientation of the sex chromosomes due to end-to-end association of the X1 and Y chromosomes, the Y and the X2 being held together by interstitial chiasmata. At metaphase II both n = 17 + Y and n = 18 + X1 are regularly observed. The two females with 2n = 37, NF = 38, are heterozygous for an autosomal centric fusion involving chromosomes 1 and 13. The product of the Y-autosome translocation constitutes the largest element of the karyotype (9.4% of the haploid set); the X1 chromosome amounts to 7.8% of this set, including a large heterochromatic block. When only its euchromatic region is considered, this percentage decreases to 4.6%. From two to seven NORs were observed at the telomeres, with a mean of 4.4 +/- 1.1 per cell.
Animals↗
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.
Asian People↗
Quantitative analysis of C-bands in chromosomes 1, 9, 16, and Y of twins.
Thirty-two pairs of Caucasoid twins, 16 monozygotic (MZ) and 16 dizygotic (DZ) of the same sex, were studied by densitometry in relation to the C-bands of chromosomes 1, 9, 16, and Y. Confirming earlier results, concordance was not absolute among MZ. Estimates of the degree of genetic determination for these traits varied from 0.73 to 0.89 for the autosomes and from 0.86 to 0.95 for the Y. There are now stronger indications that a fraction of the intergeneration variability found in these structures may be real, probably due to mitotic and/or meiotic unequal crossing-over.
Adolescent↗
Quantitative analysis of C-band size in human chromosomes.
The C-bands of chromosomes 1, 9, 16 and Y of 434 individuals were measured using densitometry. The regression coefficients observed between the length of these regions and that of lq-h varied between 0.046 and 0.189, showing a clear size effect (the larger the band, the higher the contraction per unit size). Negative regressions between the band sizes of the autosomes and the time that elapsed between fixation and band induction were also observed as well as an effect of the treatment (in average, the CBG-bands were 17% larger than the CNG ones). Appropriate methods were developed to correct for these factors. Despite that, correlations between the heterochromatic regions of chromosomes 1, 9 and 16 remained significantly positive (0.15-0.24). The y distal heterochromatin showed the same rate of contraction as the others. But it was not influenced by the slide's age or the different methods of band induction. It showed no relationship, after correction, with the C-bands of chromosomes 1 and 9, but the correlation with those of chromosomes 16 remained positive (0.25 and 0.26).
Brazil↗
Quantitative analysis of C bands in chromosomes 1, 9, and 16 of Brazilian Indians and Caucasoids.
Densitometric C-band measurements in chromosomes 1, 9, and 16 of 394 Indians and 40 Caucasoids living in Brazil are reported. No significant intratribal variability in the average length of these regions was observed, and the intertribal variation showed no consistent patterns. But the Caucasoids always presented lower means. The relative C-band sizes of these three chromosomes, however, were very similar in Indians and Caucasoids. The indices of heteromorphism displayed analogous results; only in chromosome 16 are they dissimilar in these two ethnic groups. An unexpected sex difference was observed in the C-band sizes of this chromosome, females uniformly presenting higher averages than males. Centromeric heterochromatin appeared in 6% and 9% respectively of the short arms of chromosomes 1 and 9 among the Caucasoids, while among the Indians its prevalence was 2% in both chromosomes.
Brazil↗
Familial pericentric inversion of chromosome 2.
A pericentric inversion of chromosome 2 was detected in eight members of a family ascertained via a proband with congenital jejunal atresia born of consanguineous parents. The latter affection was also present in one of his sibs. Microdensitometric analysis of the patterns of G bands of the inverted segment revealed a balanced rearrangement with unusual break points in p12 and q36; the association with the disease is apparently coincidental.
Abnormalities, Multiple↗
Chromosome studies in Brazilian rams.
A total of 127 rams from four breeds of sheep was karyotyped; 2.5 per cent had karyotype abnormalities. Two types of chromosomal variations were detected, both numerical mixopolids. From these animals, two presented a karyotype 54,XY/55,XY+mar and one 54,XY/55,XYY.
Aneuploidy↗
Effect of sex, age and cultivation time on number of satellites and acrocentric associations in man.
Lymphocyte cultures of 120 normal persons evenly distributed in relation to sex and age groups were studied. A total of 3900 cells were examined, 3600 in 3-day cultures and 300 in cultivations maintained for 2 days. In both age groups (10--13; 62--96 years) men showed higher numbers of satellites per cell but less cells with D/G associations. Older subjects presented a lower number of cells with D satellites and acrocentric associations; the pattern of these associations, however, did not seem to vary with age. The mean number of associations per cell decreased significantly in 3-day as opposed to 2-day cultures.
Adolescent↗
Senescence and human chromosome changes.
Chromosome counts and a search for structural abnormalities were performed in cultured leukocytes from 60 elderly subjects (ages 62-96) and 60 controls (ages 10-13). A total of 3900 cells were examined, 3600 in 3-day cultured and 300 in cultivations maintained for 2 days. Our results and those obtained by other investigators indicate clearly that there is an increase in the level of aneuploidy and of structural abnormalities in the blood of aged persons. There is an excess of missing C-group chromosomes in elderly females, but no consistent preferential loss was observed among the males. In contrast with two previous studies, we found a significant decrease of aneuploid cells in 3-day cultures, as compared to those cultivated for 2 days only.
Adolescent↗
Chromosome studies in patients with congenital malformations and mental retardation.
16 (41%) out of 39 individuals referred by physicians because of sexual anomalies showed abnormal karyotypes; the corresponding figure for those investigated due to suspected autosomal aberrations was 37 out of 104 (36%). A special survey was also conducted among 51 mentally defective children with at least 3 malformations; 5 individuals (10%) were observed with chromosome abnormalities plus 3(6%) with rare variants. These results were compared with those presented in 26 other surveys reported in the literature.
Abnormalities, Multiple↗
Cytogenetic, clinical and genealogical analyses in a series of gonadal dysgenesis patients and their families.
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Abnormalities, Multiple↗
Size variability of the Y chromosome distal C-band in Brazilian Indians and Caucasoids.
Densitometric measurements of the Y chromosome distal heterochromatin were performed on 183 Indians and 21 Caucasoids living in Brazil. No significant intratribal intervillage variation was observed, but the tribal averages were different, ranging from 0.81 to 1.32 mu. The Caucasoid mean presented an intermediate value. Wide intrapopulation variability occurs, as well as a suggestion of bimodality in the measurements obtained among the Indians of the Amazon region. Surprisingly a positive correlation was found between this variable and the C-band size of chromosome 16, as well as between it and the heteromorphism index of chromosome 1.
Adult↗
A cytogenetic survey of five breeds of cattle from Brazil.
One-hundred-and-thirty-nine animals from five breeds of cattle were studied cytogenetically. Three types of karyotype abnormalities were detected, two of them structural, t(1; 29) and ins(16), and one numerical (60,XY/61,XY + F). The first two, found in the Charolais race, presented familial recurrences; the last one, observed in the Norman breed, was sporadic. Pedigree studies showed that ins(16), an aberration not previously described in cattle, segregated in the ratio of 5 carriers to 10 normals. t(1; 29) occurred in mother and daughter. A variant of constitutive heterochromatin also presented familial recurrence in the Charolais breed.
Animals↗