Illustration of the gene (orange) located on the long arm of the X-chromosome. FMR1 codes for the protein fragile x mental retardation protein (FMRP). A member of the nuclear ribonucleoprotein family of RNA (ribonucleic acid)-binding proteins, FMRP regulates transport and represses translation of a subset of neuronal mRNAs (messenger RNAs). Mutations within this gene segment are associated with the disease fragile x syndrome (FXS).