Abstract
IN man, dosage compensation is achieved by random genetic inactivation of one X chromosome in each female cell early in embryonic life1; all descendants of this X chromosome then remain genetically inactive. The inactive X chromosome is late replicating and manifests itself as a sex chromatin body in the interphase somatic nuclei of females2,3. Because sex chromatin appears in human embryos approximately 12 days after conception4, it is presumed—although not certain—that X inactivation (Lyonization)5 occurs at this time. All human X-linked loci which have been tested hitherto have shown evidence of dosage compensation1. It is significant, however, that with one exception all these studies have been on older children or adults. A problem with the Lyon hypothesis is the existence of clinical abnormalities, particularly those of a non-sex-related nature, in patients with an abnormal number of X chromosomes. It suggests1,6 either that great damage can be done to human development by an abnormal number of X chromosomes before X-inactivation or that at least some X-linked loci must escape dosage compensation to a significant extent. This study supports the latter concept.
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STEELE, M. Incomplete Dosage Compensation for Glucose-6-phosphate Dehydrogenase in Human Embryos and Newborns. Nature 227, 496–498 (1970). https://doi.org/10.1038/227496a0
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DOI: https://doi.org/10.1038/227496a0
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