Summary
We have analysed two duplications of the X chromosome in male patients using chromosome replication and DNA methylation patterns as determinants of the functional status of the duplicated segments. In both cases, the large duplicated regions, Xq12-q22 and Xq26.3-qter, were not inactivated. A review of previously reported male cases revealed that these duplications were also not subject to inactivation. Taken together, the examined duplications cover almost the entire X chromosome except the pericentromeric region and Xq25–26. Thus, most regions of the X chromosome can be present in two functional copies without lethal consequences.
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Schmidt, M., Du Sart, D., Kalitsis, P. et al. Duplications of the X chromosome in males: evidence that most parts of the X chromosome can be active in two copies. Hum Genet 86, 519–521 (1991). https://doi.org/10.1007/BF00194646
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DOI: https://doi.org/10.1007/BF00194646