This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
The FMR1 protein 
Select and explain. 
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
D: Is coded by the FMR1 gene which has the (5′-CGG-3′) n repeat segments
Answer: D: Is coded by the FMR1 gene which has the (5′-CGG-3′) n repeat segments 
Explanation: 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.