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: Medicine
[{'content': 'Fragile X-syndrome is characterized by all of the following except - \nSelect and explain. \nA. Long face, B. Large ear, C. Large nose, D. Large testis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Fragile X - syndrome\n\nIt is caused by Triplet repeat mutations, the mutations are characterized by a long repeating sequence of three nucleotides.\nIt is an X-linked disorder characterized by an inducible cytogenetic abnormality in the X-chromosome.\nThe cytogenetic abnormality is seen as a discontinuity of staining or as a constriction in the long arm of the X chromosome.\nBecause it appears that the chromosome is "broken" at this locale, it is referred to the as fragile site.\n\nClinical features\n\nFragile X syndrome is the second most common genetic cause of mental retardation, after Down\'s syndrome.\nIn this syndrome, the affected males are mentally retarded with I.Q. in the range of 20 - 60. These patients express a characteristic phenotype that includes\nLong face with long mandible\nLarge everted ears\nLarge testicles (macroorchidism)\nHyperextensible joints, high arched palate and mitral valve prolapse.\nThese and other physical abnormalities described in this condition, however, are not always present and in some cases are quite subtle.\nThe only distinctive feature that can be detected in at least 90% of postpubertal males with fragile X-syndrome is macro-orchidism.\nAs with all X linked diseases, fragile X syndromes affects males.', 'role': 'assistant'}]