脆性X综合征FMR—1基因CGG重复数变异的研究

The Study of the Variation of CGG Repeat in FMR - 1 Gene of Fragile X Syndrome.

采用PCR凝胶电泳法测定126条正常人群X染色体及来源于脆性X综合征家族的18条染色体的P(CGG)n重复数目。结果:①正常人群中,CGG重复数目最多为28,变动范围21～41(CGG)。FMR-1基因可稳定扩增,且后代受损程度不一。②脆性X家族中,母亲均为正常传递携带者,她们的前突变在卵子减数分裂过程中转变为全突变,从而导致了患病后代。脆性X综合征最罕见的遗传特点是存在正常传递男子,而且他的前突变可通过其女儿传至其孙子及曾孙。因此研究正常男、女性传递者具有临床价值。本方法简单、易行,可用于高危群体的筛查,同时也为遗传咨询和优生优育产前诊断提供依据。

In the article, we used PCR - gel elec-trophoresis method to determine the number of repeat of P(CGG) n.We have 126 normal X chromosomes and 18 X chromosomes obtained from fra (X)families.The result implies ①In normal people, the most mean number of CGG repeat is (CGG) 28, the normal range is (CGG) 21- (CGG) 41. In normal individuals the FMR - 1 gene expands in stable fashion, from the parent to offsprings. ② In Fragile X individuals, the repeated sequences not only expand abnormally but are unstable and the degree ofimpairment in offspring may vary. In fra(X) families, all mothers are normal transmitting females, their pre-mutation turns to full mutation during the process of meiosis of the ovum, thus it leads to abnormal offsprings. The rare genetic character of fra(X) is that there are NTFs and NTMs, their pre - mutation may be transmitted to their grandsons and great - grandsons through their daugh-ters. ③The study of NTFs and NTMs has great clinical value. ④ The method is simple and easy to be performed.It can be used in screening in the high - risk people. It also gives an evidence for clinical genetic counseling and prenatal diagnosis.