Fragile X syndrome (FXS) is the most common inherited form mental impairment that is caused by an expanded CGG trinucleotide repeat in the 5′ untranslated region of the fragile X mental retardation (FMR1) gene leading to gene silencing and loss of the fragile X mental retardation protein (FMRP) [51–55]. This evidence concerns the gene FMR1 and fragile X syndrome.