Eichler E E, Holden J J, Popovich B W, Reiss A L, Snow K, Thibodeau S N, Richards C S, Ward P A, Nelson D L
Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, Texas 77030.
Nat Genet. 1994 Sep;8(1):88-94. doi: 10.1038/ng0994-88.
Analysis of 84 human X chromosomes for the presence of interrupting AGG trinucleotides within the CGG repeat tract of the FMR1 gene revealed that most alleles possess two interspersed AGGs and that the longest tract of uninterrupted CGG repeats is usually found at the 3' end. Variation in the length of the repeat appears polar. Alleles containing between 34 and 55 repeats, with documented unstable transmissions, were shown to have lost one or both AGG interruptions. These comparisons define an instability threshold of 34-38 uninterrupted CGG repeats. Analysis of premutation alleles in Fragile X syndrome carriers reveals that 70% of these alleles contain a single AGG interruption. These data suggest that the loss of an AGG is an important mutational event in the generation of unstable alleles predisposed to the Fragile X syndrome.
对84条人类X染色体进行分析，以检测FMR1基因CGG重复序列中是否存在中断的AGG三核苷酸，结果显示大多数等位基因有两个散布的AGG，并且最长的不间断CGG重复序列通常位于3'端。重复序列长度的变化似乎具有极性。已证明含有34至55个重复序列且有不稳定传递记录的等位基因失去了一个或两个AGG中断。这些比较确定了34 - 38个不间断CGG重复序列的不稳定阈值。对脆性X综合征携带者的前突变等位基因分析表明，这些等位基因中有70%含有单个AGG中断。这些数据表明，AGG的缺失是产生易患脆性X综合征的不稳定等位基因的重要突变事件。
