赖昂假说认为,在雌性哺乳动物体细胞中,有一条X染色体高度固缩,在遗传上没有功能。以后,这个假说得到多方面的证实。关于X染色体失活的一个解释是该染色体在甲基化后抑制了染色体上基因的活性。所以对人卵原细胞中的甲基化现象进行了研究,以弄清楚当X染色体出现失活时,其胚胎发育的真实情况如何。 The Lyon hypothesis states that in the body cells of female mammals, there is a highly condensed X chromosome that is genetically non-functional. Later, this hypothesis was confirmed in many aspects. One explanation for the inactivation of the X chromosome is that the chromosome inhibits the activity of the gene on the chromosome after methylation. Therefore, the phenomenon of methylation in human oogonia cells was studied to find out the true situation of embryo development when the X chromosome was inactivated.