Review Article

Human Genetics

, Volume 126, Issue 3, pp 363-373

First online:

X chromosome inactivation in clinical practice

  • Karen Helene ØrstavikAffiliated withDepartment of Medical Genetics, Oslo University Hospital, Rikshospitalet and Faculty Division Rikshospitalet, University of Oslo Email author 

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X chromosome inactivation (XCI) is the transcriptional silencing of the majority of genes on one of the two X chromosomes in mammalian females. Females are, therefore, mosaics for two cell lines, one with the maternal X and one with the paternal X as the active chromosome. The relative proportion of the two cell lines, the X inactivation pattern, may be analyzed by simple assays in DNA from available tissues. This review focuses on medical issues related to XCI in X-linked disorders, and on the value of X inactivation analysis in clinical practice.