脆性X综合征是导致遗传性智力障碍的一种最常见的形式,它是由位于Xq27.3处的一种特殊DNA片段突变即其大小增加所导致的。患者体内的这种DNA片段有两种改变,一种是完全突变,另一种是不正常的DNA甲基化。如果这种片段的大小改变比较小(预突变),则临床上只有轻微症状,或没有症状,但是其后代则有很大风险患此病。这种从预突变到完全突变的传递仅仅发生于母亲向后代的传递。作者找到一种直接DNA分析方法来鉴别这些突变的携带者。作者从63个脆性X综合征家系中的511个个体的白细胞中提取DNA,然后采用EcoRI和EagI进行双酶切,Southern转移,最后用与突变位点邻近的atB12.3探针 Fragile X syndrome is one of the most common forms of genetic dementia that results from a specific DNA fragment mutation at Xq27.3, ie, an increase in its size. There are two changes in this DNA fragment in patients, one is complete mutation, the other is abnormal DNA methylation. If the size of the fragment changes relatively small (pre-mutation), then there are only mild or clinically clinically relevant symptoms, but its offspring have a high risk of developing the disease. This transfer from pre-mutation to complete mutation occurs only from mother to offspring. The authors found a direct DNA analysis to identify carriers of these mutations. The authors extracted DNA from white blood cells of 511 individuals in 63 Fragile X syndrome families and then double-digested them with EcoRI and EagI and Southern blotted them down with atB12.3 probe adjacent to the mutation site