Variable CGG repeat expansions in the 5′ untranslated portion of the fragile mental retardation 1 gene (FMR1, chrXq27.3) cause a spectrum of disorders, including fragile X syndrome (FXS, OMIM # 300624) (>200 CGG repeats), fragile X-associated tremor ataxia syndrome (FXTAS, OMIM # 300623; permutation 55–200 CGG repeats), and fragile X-associated primary ovarian insufficiency (FXPOI, premutation) [104]. This evidence concerns the gene FMR1 and fragile X syndrome.