在雌性哺乳动物的体细胞中，两条X染色体中的一条总是被异染色质化而失活，这个现象称为X染色体失活。X染色体失活保证了性染色体上的基因剂量在雌性和雄性动物之间的平衡。它是许多生物学现象和疾病的生物学基础。本文简要介绍了X染色体失活的现象，基本生物学概念以及潜在机理，最后介绍了与之相关的疾病，例如X染色体数量异常和伴性遗传疾病的病理知识。

In female mammals’ body cells, one of the X-chromosomes is inactivated as heterochromatin to balance the expression of X-linked genes in females and males. This is so called X chromosome inactivation, the biological basis of many biological phenomena and diseases. Here, we briefly review the phenomena, the basic knowledge of the X chromosome inactivation and the connections to disease.