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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 infertile males and in males with sex-chromosome abnormalities (usually with very low numbers of spermatozoa) the results show an increased incidence of sex chromosome aneuploidies and diploid (multi-aneuploid?) sperm nuclei.
Abstract: The use of chromosome specific DNA probes labelled with fluorochromes and especially the combination of several probes has been used to indirectly study the chromosome constitution of decondensed sperm nuclei by fluorescence in-situ hybridization (FISH), and has allowed to include this test in the protocol of study of infertile males. Still, if the test is to be valid, several strict conditions must be met, and some specific characteristics have to be taken into account. This becomes evident when comparing earlier results with more recent ones. The basic technical factors to be taken into account are the methods of chromatin decondensation, the number of spermatozoa and of individuals to study, the use of internal controls, the scoring criteria, the specificity of the probes and the possible existence of polymorphisms that may interfere with the detection of fluorescent signals. In the last 7 or 8 years, a large number of papers has been published, describing the incidence of aneuploidies in controls, in individuals in whom a tendency to non-disjunction was suspected and in infertile males. Studies in controls have shown a considerable intra- and inter-individual variability in the frequency of aneuploidies, the tendency of some chromosomes to undergo non-disjunction (chromosome 21 and the sex chromosomes) and the importance of alpha-satellite polymorphisms when using centromere probes. In the control population, the frequency of aneuploidy per haploid set has been estimated at approximately 6%. The incidence of aneuploidies in sperm nuclei for some of the chromosomes more frequently involved in trisomies is considerably higher than the incidence of these trisomies established through epidemiological data using the global incidence of chromosome abnormalities during the peri-implantation stage. In infertile males and in males with sex-chromosome abnormalities (usually with very low numbers of spermatozoa) the results show an increased incidence of sex chromosome aneuploidies and diploid (multi-aneuploid?) sperm nuclei. The results could be related to the higher incidence of chromosome abnormalities (especially sex-chromosome aneuploidies) observed in children conceived by intracytoplasmic sperm injection (ICSI).

159 citations

Journal ArticleDOI
01 Mar 1983-Nature
TL;DR: The localization of a gene to the tip of the short arm of the human X chromosome and evidence for a related gene on the Y chromosome is described.
Abstract: The mammalian sex chromosomes are thought to be related to each other by sharing a common origin. That is, the X and Y chromosomes originally evolved from a pair of chromosomes that only differed at the locus determining sexual differentiation1,2. For example, this evolutionary relationship is reflected during meiosis3 in chromosomal pairing between the tip of the human X chromosome short arm and the Y chromosome which presumably implies sequence homology4. However, compelling genetic evidence for functional homology between the mammalian X and Y chromosome is lacking. We describe here the localization of a gene to the tip of the short arm of the human X chromosome and evidence for a related gene on the Y chromosome.

159 citations

Journal ArticleDOI
TL;DR: The data suggest that the locus alpha 21-I containing regularly spaced CENP-B boxes at high-frequency and the assembly site of the centromere antigens may be involved in common centROMere function in both human and mouse cells.
Abstract: The long-range organization of alphoid DNA arrays of human chromosome 21 was investigated using a mouse-human somatic cell hybrid. Two distinct long alphoid DNA arrays, the loci alpha 21-I and alpha 21-II, were identified in the centromere region of human chromosome 21. The alpha 21-I locus, composed of an array of 11 monomer repeat units (the 11 mer), was estimated to have a total length of 1.3 Mbp. CENP-B boxes, the binding sites of the centromere protein B (CENP-B), appeared in every other monomer unit in the 11 mer except for one place where two monomer units were repeated without any CENP-B box. The other locus, alpha 21-II, was found to be composed of alphoid subfamilies with low homology to the components of alpha 21-I locus. Five different alphoid clones presenting 32 monomer units in total were isolated from the alpha 21-II locus. Sequences of these monomer units diverged between 71-89% and no unit containing a CENP-B box was found. By analysis using two color FISH, the alpha 21-I was localized to the primary constriction, whereas the alpha 21-II site was located slightly to the short arm side. Furthermore, a combination of FISH and immunofluorescent staining indicated that the alpha 21-I site was co-localized and overlapped with the CREST centromere antigenic site on mitotic chromosomes and in interphase nuclei, while alpha 21-II was distributed broadly. Our data suggest that the locus alpha 21-I containing regularly spaced CENP-B boxes at high-frequency and the assembly site of the centromere antigens may be involved in common centromere function in both human and mouse cells.

158 citations

Journal ArticleDOI
01 Apr 2001-Genetics
TL;DR: This physical map of rice chromosome 10 developed by fluorescence in situ hybridization (FISH) mapping of bacterial artificial chromosome (BAC) clones on meiotic pachytene chromosomes reveals the precise genetic position of the centromere on chromosome 10.
Abstract: Large-scale physical mapping has been a major challenge for plant geneticists due to the lack of techniques that are widely affordable and can be applied to different species. Here we present a physical map of rice chromosome 10 developed by fluorescence in situ hybridization (FISH) mapping of bacterial artificial chromosome (BAC) clones on meiotic pachytene chromosomes. This physical map is fully integrated with a genetic linkage map of rice chromosome 10 because each BAC clone is anchored by a genetically mapped restriction fragment length polymorphism marker. The pachytene chromosome-based FISH mapping shows a superior resolving power compared to the somatic metaphase chromosome-based methods. The telomere-centromere orientation of DNA clones separated by 40 kb can be resolved on early pachytene chromosomes. Genetic recombination is generally evenly distributed along rice chromosome 10. However, the highly heterochromatic short arm shows a lower recombination frequency than the largely euchromatic long arm. Suppression of recombination was found in the centromeric region, but the affected region is far smaller than those reported in wheat and barley. Our FISH mapping effort also revealed the precise genetic position of the centromere on chromosome 10.

158 citations

Journal ArticleDOI
TL;DR: Reduced genetic recombination may be responsible, at least in part, for the association between advancing maternal age and trisomy 21.
Abstract: Over 300 cases of trisomy 21 were analyzed to characterize the causes of maternal non-disjunction and to evaluate the basis for maternal age-dependent trisomy 21. We confirmed the observation that recombination along 21q is reduced among non-disjoined chromosomes 21 and further demonstrated that the alterations in recombination are restricted to meiosis I origin. Analysis of the crossover distribution indicates that reduction in recombination is not due simply to failure of pairing and/or absence of recombination in a proportion of cases. Instead, we observed an increase in both zero- and one-exchange events among trisomy 21-generating meioses suggesting that an overall reduction in recombination may be the underlying cause of non-disjunction. Lastly, we observed an age-related reduction in recombination among the meiosis I cases, with older women having less recombination along 21q than younger women. Thus, reduced genetic recombination may be responsible, at least in part, for the association between advancing maternal age and trisomy 21.

157 citations


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