McDermott A, Walters R, Howell R T, Gardner A
J Med Genet. 1983 Jun;20(3):169-78. doi: 10.1136/jmg.20.3.169.
Results of detailed clinical and cytogenetic studies on 13 mentally retarded males and two heterozygous females (one normal and one retarded) are reported. Reference is made to technical modifications to enhance the incidence of expression of the fragile X. The addition of excess methionine to the fibroblast cultures (final concentration of 115 mg/l medium TC 199) was found to be particularly valuable, increasing the incidence of expression up to four-fold, and enabling the demonstration of the fragile X in fibroblasts when it could not be demonstrated in blood cultures in at least one case. Studies on replication patterns of the X chromosomes in the two heterozygous females showed that the fragile X chromosome was genetically active in a significantly greater proportion of cells (74%) in the mentally retarded female, whereas the normal X was active in a similar proportion (72%) in the carrier with normal intelligence.
报告了对13名智力迟钝男性和两名杂合子女性（一名正常，一名智力迟钝）进行的详细临床和细胞遗传学研究结果。文中提及了为提高脆性X表达发生率所做的技术改进。发现向成纤维细胞培养物中添加过量蛋氨酸（最终浓度为每升TC 199培养基115毫克）特别有价值，可将表达发生率提高四倍，并能在至少一例血液培养中无法显示脆性X时，在成纤维细胞中显示出脆性X。对两名杂合子女性X染色体复制模式的研究表明，在智力迟钝女性中，脆性X染色体在显著更多比例的细胞（74%）中具有遗传活性，而在智力正常的携带者中，正常X染色体在相似比例（72%）的细胞中具有活性。
