Fragile X Syndrome (FXS) is a genetic cause of intellectual disability (Crawford et al., 2001) that results from a mutation in the Fragile X Mental Retardation 1 (Fmr1) gene and down-regulation of Fragile X Mental Retardation Protein (FMRP) (Yu et al., 1991). The gene discussed is FMR1; the disease is fragile X syndrome.