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: Pediatrics
[{'content': 'Which is not true about Fragile X syndrome? \nSelect and explain. \nA. Large testis, B. Pigmented nevi, C. Large ear present, D. No large nose', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Fragile - X syndrome \n\nFragile - X syndrome is the prototype of diseases in which the mutation is characterized by a long repeating sequence of three nucleotides.\nIn fragile X syndrome, trinucleotide repeat mutation involves CGG on the non-coding region.\n\nClinical features of fragile - X syndrome\n\nMental retardation \xa0\nLong face with large mandible\nHyperextensible joint\xa0\nMitral valve prolapse\nLarge everted ears\nLarge testis (macroorchidism)\xa0\nHigh arched palate\xa0 \xa0 \xa0 \xa0\nFragile X syndrome is the second most common cause of mental retardation, after Downs syndrome.', 'role': 'assistant'}]