Cytosine-guanine-guanine (CGG) trinucleotide repeat expansion in the 5′ untranslated region of Fragile X mental retardation 1 (FMR1) gene over 200 and the consequent lack of protein product, Fragile X protein [FXP, formerly referred to as Fragile X mental retardation protein (FMRP)], results in a “full mutation,” clinically Fragile X Syndrome (FXS), whereas 55–200 repeats results in what is called a “premutation” (Pieretti et al., 1991; Verkerk et al., 1991). This evidence concerns the gene FMR1 and fragile X syndrome.