Topic
X chromosome
About: X chromosome is a research topic. Over the lifetime, 9862 publications have been published within this topic receiving 407354 citations. The topic is also known as: GO:0000805 & chrX.
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TL;DR: Clinical and animal studies indicate that male hormones suppress autoantibody production whereas female hormones support their production, and Superior immunocompetence and survival of females is based, in part, on their being protected from mutant immunoregulatory genes located on the X chromosome.
Abstract: Evolutionary selection has equipped females with immunoregulatory genes on the X chromosome for coping with life-threatening illness. Five immunodeficiency syndromes occur solely in males, suggesting that they arise from mutant immunoregulatory genes located on the X chromosome. These syndromes, although rare, could contribute to poorer survival of males. Females have higher serum IgM concentrations, superior ability to form antibodies to infectious agents, and experience a lower incidence of viral and bacterial infectious diseases. Preponderance of autoimmune disorders in females could arise from modified immune responses owing to estrogens. Clinical and animal studies indicate that male hormones suppress autoantibody production whereas female hormones support their production. Superior immunocompetence and survival of females is based, in part, on their being protected from mutant immunoregulatory genes located on the X chromosome.
107 citations
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TL;DR: The distribution of chromosome loss in the hypohaploid complements indicated that significantly fewer of the large chromosomes and significantly more of the small chromosomes were lost, suggesting that technical loss predominantly affects small chromosomes.
Abstract: The human sperm/hamster egg fusion technique has been used to analyse 6,821 human sperm chromosome complements from 98 men to determine if all chromosomes are equally likely to be involved in aneuploid events or if some chromosomes are particularly susceptible to nondisjunction. The frequency of hypohaploidy and hyperhaploidy was compared among different chromosome groups and individual chromosomes. In general, hypohaploid sperm complements were more frequent than hyperhaploid complements. The distribution of chromosome loss in the hypohaploid complements indicated that significantly fewer of the large chromosomes and significantly more of the small chromosomes were lost, suggesting that technical loss predominantly affects small chromosomes. Among the autosomes, the observed frequency of hyperhaploid sperm equalled the expected frequency (assuming an equal frequency of nondisjunction for all chromosomes) for all chromosome groups. Among individual autosomes, only chromosome 9 showed an increased frequency of hyperhaploidy. The sex chromosomes also showed a significant increase in the frequency of hyperhaploidy. These results are consistent with studies of spontaneous abortions and liveborns demonstrating that aneuploidy for the sex chromosomes is caused by paternal meiotic error more commonly than aneuploidy for the autosomes.
107 citations
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TL;DR: A linkage study in 30 Becker muscular dystrophy kindreds using three cloned DNA sequences from the X chromosome which demonstrate restriction fragment length polymorphisms (RFLPs), suggests that the BMD gene is located on the short arm of the X chromosomes, in the p21 region.
Abstract: A linkage study in 30 Becker muscular dystrophy (BMD) kindreds using three cloned DNA sequences from the X chromosome which demonstrate restriction fragment length polymorphisms (RFLPs), suggests that the BMD gene is located on the short arm of the X chromosome, in the p21 region. The genes for Becker and Duchenne dystrophies must therefore be closely linked, if not allelic, and any future DNA probes found to be of practical use in one disorder should be equally applicable to the other. The linkage analysis also provides data on the frequency of recombination along the short arm of the X chromosome, and across the centromeric region.
107 citations
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University of Brescia1, University of Oslo2, Nancy-Université3, John Radcliffe Hospital4, University of Padua5, Royal Free Hospital6, Necker-Enfants Malades Hospital7, University of Haifa8, Karolinska Institutet9, University of Helsinki10, Robert Koch Institute11, Soroka Medical Center12, University of Pavia13, Casa Sollievo della Sofferenza14, University of Turin15, Leiden University16, University of Washington17, Keio University18, Boston Children's Hospital19, Mitsubishi20
TL;DR: A database (CD40Lbase) of CD40L mutations has now been established, and the resultant information, together with other mutations reported elsewhere in the literature, is presented here.
107 citations
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TL;DR: It is proposed that the MSCI and the MSYq-dependent gonosomal repression in spermatids are evolutionary adaptations to maintain a normal sex ratio in the face of X/Y antagonism.
Abstract: Deletions on the mouse Y-chromosome long arm (MSYq) lead to teratozoospermia and in severe cases to infertility. We find that the downstream transcriptional changes in the testis resulting from the loss of MSYq-encoded transcripts involve upregulation of multiple X- and Y-linked spermatid-expressed genes, but not related autosomal genes. Therefore, this indicates that in normal males, there is a specific repression of X and Y (gonosomal) transcription in post-meiotic cells, which depends on MSYq-encoded transcripts. Together with the known sex ratio skew in favour of females in the offspring of fertile MSYqdel males, this strongly suggests the existence of an intragenomic conflict between X- and Y-linked genes. Two potential antagonists in this conflict are the X-linked multicopy gene Xmr and its multicopy MSYq-linked relative Sly, which are upregulated and downregulated, respectively, in the testes of MSYqdel males. Xmr is also expressed during meiotic sex chromosome inactivation (MSCI), indicating a link between the MSCI and the MSYq-dependent gonosomal repression in spermatids. We therefore propose that this repression and MSCI itself are evolutionary adaptations to maintain a normal sex ratio in the face of X/Y antagonism.
107 citations