Nancarrow J K, Holman K, Mangelsdorf M, Hori T, Denton M, Sutherland G R, Richards R I
Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, North Adelaide, Australia.
Hum Mol Genet. 1995 Mar;4(3):367-72. doi: 10.1093/hmg/4.3.367.
Rare, folate-sensitive fragile sites are the result of the unstable expansion of trinucleotide p(CCG)n repeats, which are normally polymorphic in copy number. Differences in the number and frequency of alleles of the fragile site FRA16A p(CCG)n repeat were observed between different ethnic populations suggesting that certain alleles might be predisposed to instability. Sequence analysis demonstrated that the longer and more variable alleles were associated with loss of repeat interruption. Perfect repeat configuration therefore appears to be a necessary precondition for the instability associated with fragile site genesis.
罕见的、对叶酸敏感的脆性位点是三核苷酸p(CCG)n重复序列不稳定扩增的结果，这些重复序列在拷贝数上通常具有多态性。在不同种族人群之间观察到脆性位点FRA16A p(CCG)n重复序列的等位基因数量和频率存在差异，这表明某些等位基因可能易于发生不稳定。序列分析表明，较长且更具变异性的等位基因与重复序列中断的缺失有关。因此，完美的重复序列构型似乎是与脆性位点发生相关的不稳定的必要先决条件。
