The FMR1 protein: (A) Is expressed in fragile X-associated mental retardation, (B) Is normally found in brain and ovaries, (C) When defective, is not sufficient to cause the fragile X-associated mental retardation syndrome, (D) Is coded by the FMR1 gene which has the (5′-CGG-3′) n repeat segments
Answer is D. The family mental retardation (FMR1) protein is normally expressed in brain and testes. It is encoded by the FMR1 gene. Amplification of the CGG region to a repeat number greater than 200 causes methylation of the CpG is land and prevents the FMR1 protein from being expressed. This defect is sufficient to cause the fragile X-associated mental retardation syndrome.