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Chromosome 21

About: Chromosome 21 is a research topic. Over the lifetime, 4736 publications have been published within this topic receiving 206655 citations. The topic is also known as: chr21 & Homo sapiens chromosome 21.


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Journal ArticleDOI
TL;DR: In this study, multicolor fluorescence in situ hybridization was used to determine levels of disomy for the clinically relevant chromosomes X, Y, 13, 18, and 21 in 332,858 spermatozoa from nine reciprocal translocation heterozygotes and nine controls with normal karyotypes.
Abstract: Chromosome translocations have been known to affect disjunction of chromosomes unrelated to the translocation in the mouse and in Drosophila. However, in humans, an interchromosomal effect in chromosome translocations has not been demonstrated. The availability of techniques that allow the study of nondisjunction in sperm cells has permitted us to evaluate the possibility of an interchromosomal effect in male translocation heterozygotes. In this study, multicolor fluorescence in situ hybridization was used to determine levels of disomy for the clinically relevant chromosomes X, Y, 13, 18, and 21 in 332,858 spermatozoa from nine reciprocal translocation heterozygotes and nine controls with normal karyotypes. The specific translocations studied were as follows: t(10;12)(p26.1;p13.3), t(2;18)(p21;q11.2), t(3;19)(p25;q12), t(5;8)(q33;q13), t(11;22)(q23;q11), t(3;4)(p25;p16), t(8;9)(q24.2;q32), t(10;18)(q24.1;p11.2), and t(4;10)(q33;p12.2). Comparisons of disomy rates between carriers and controls were performed by using the Mann-Whitney test. Our results showed that the rates of sex chromosome hyperhaploidy were similar in controls (0.21%) and in translocation carriers (0.19%). Similarly, the frequencies of disomy for chromosomes 13, 18, and 21 did not differ significantly between controls and carriers (0.05% versus 0.08%, 0.07% versus 0.03%, and 0.14% versus 0.20%, respectively). Sex chromosome nondisjunction was more common than nondisjunction of chromosomes 13 and 18 both in controls (P=0.0057) and in carriers (P=0.0008). Similarly, the rates of chromosome disomy for chromosome 21 were higher than those for chromosomes 13 and 18 in both controls (P=0.0031) and translocation carriers (P=0.0057). In our study, the excess of chromosome 21 disomy versus disomy of the other autosomes was more pronounced in carriers than in controls. Thus, although the difference of disomy 21 between controls and carriers was not statistically significant, it is worthy of attention.

72 citations

Journal Article
TL;DR: Results indicate that the chromosome 14 locus is not responsible for Alzheimer disease in most late-onset FAD kindreds but could play a role in a subset of these kindreds.
Abstract: Familial Alzheimer disease (FAD) is genetically heterogeneous. Two loci responsible for early-onset FAD have been identified: the amyloid precursor protein gene on chromosome 21 and the as-yet-unidentified locus on chromosome 14. The genetics of late-onset FAD is unresolved. Maximum-likelihood, affected-pedigree-member (APM), and sib-pair analyses were used, in 49 families with a mean age at onset ≥60 years, to determine whether the chromosome 14 locus is responsible for late-onset FAD. The markers used were D14S53, D14S43, and D14S52. The LOD score method was used to test for linkage of late-onset FAD to the chromosome 14 markers, under three different models: age-dependent penetrance, an affected-only analysis, and age-dependent penetrance with allowance for possible age-dependent sporadic cases. No evidence for linkage was obtained under any of these conditions for the late-onset kindreds, and strong evidence against linkage (LOD score ≤ –2.0) to this region was obtained. Heterogeneity tests of the LOD score results for the combined group of families (early onset, Volga Germans, and late onset) favored the hypothesis of linkage to chromosome 14 with genetic heterogeneity. The positive results are primarily from early-onset families. APM analysis gave significant evidence for linkage of D14S43 and D14S52 to FAD in early-onset kindreds (P < .02). No evidence for linkage was found for the entire late-onset family group. Significant evidence for linkage to D14S52, however, was found for a subgroup of families of intermediate age at onset (mean age at onset ≥60 years and <70 years). These results indicate that the chromosome 14 locus is not responsible for Alzheimer disease in most late-onset FAD kindreds but could play a role in a subset of these kindreds.

72 citations

Journal ArticleDOI
TL;DR: Flattened metaphase figures were obtained by squashing or air-drying cells from human leucocyte cultures that had been treated with colchicine and hypotonic sodium citrate prior to fixation to find the Y chromosome at the periphery of the figure more often than chance expectation.
Abstract: Flattened metaphase figures were obtained by squashing or air-drying cells from human leucocyte cultures that had been treated with colchicine and hypotonic sodium citrate prior to fixation. In such metaphase figures the Y chromosome was at the periphery of the figure more often than chance expectation and more often than the chromosome pairs 1, 2, or 16 or the chromosome groups 13–15, 17–18, 19–20, or 21–22. The Y chromosome was further from the center of circular metaphase figures than the mean value of all the chromosomes or the chromosome pairs 1, 2, or 3 or the chromosome groups 4–5, 6–12+X, 19–20 or 21–22.

72 citations

Journal ArticleDOI
J. L. Hamerton1
31 Aug 1968-Nature
TL;DR: One mammalian X chromosome in females and the Y chromosome in males are heterochromatic, and they seem to carry “controlling centers” which affect both sex determination and various somatic characters.
Abstract: One mammalian X chromosome in females and the Y chromosome in males are heterochromatic, and they seem to carry “controlling centers” which affect both sex determination and various somatic characters. The euchromatic X chromosome may carry the structural genes for testicular as well as ovarian determination, the former only functioning in the presence of a Y chromosome or suitable autosomal modifier.

72 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202259
202147
202061
201943
201858