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': 'Genetic abnormality in fragile x syndrome- \nSelect and explain. \nA. Trinucleotide repeats, B. Point mutation, C. Not inheritable, D. Deletion', 'role': 'user'}, {'content': "Answer: A \nExplanation: Fragile X syndrome is the prototype of diseases in which the mutation is characterized by a long repeating sequence of 3 nucleotides.\nThese mutations are characterized by amplification of a sequence of three nucleotides.\nAlthough the specific nucleotide sequence that undergoes amplification differs in various disorders, almost all affected sequences share the nucleotides Guanine (G) and cytosine (C).\n\nAlso, know -\n\nIt is the second most common cause of mental retardation after Down's syndrome.\nIt is an X linked disorder characterized by an inducible cytogenetic abnormality in the X chromosome and an unusual mutation within the familial mental retardation (-1 FMR-1 gene).\n\nTrinucleotide Repeat disorders\n\nExpansions affecting the non-coding region\nFragile X syndrome\nFrederich's ataxia\nMyotonic dystrophy\n\nExpansions affecting coding region\n\nSpinobulbar muscular atrophy\nHuntington's disease\nDentatorubral pallidoluysian\nSpinocerebellar ataxia type 1\nSpinocerebellar ataxia type 2\nSpinocerebellar ataxia type 3\nSpinocerebellar ataxia type 6\nSpinocerebellar ataxia type 7", 'role': 'assistant'}]