Unique AGG Interruption in the CGG Repeats of the FMR1 Gene Exclusively Found in Asians Linked to a Specific SNP Haplotype.

Fragile X syndrome (FXS) is the most common inherited intellectual disability. It is caused by the occurrence of more than 200 pure CGG repeats in the FMR1 gene. Normal individuals have 6-54 CGG repeats with two or more stabilizing AGG interruptions occurring once every 9- or 10-CGG-repeat blocks in various populations.