FMR1 and fragile X syndrome: Fragile X-associated disorders are caused by a CGG repeat expansion in the 5’ untranslated region (5’ UTR) of the FMR1 gene, including fragile X-associated tremor/ataxia syndrome (FXTAS), of which the number of CGG is among 55–199 (premutation range) and fragile X syndrome (FXS) of which the number of CGG is over 200 (full mutation range) (Hagerman and Hagerman, 2021).