This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
[{'content': 'Increasing severity of mental retardation of male members over generations is a result of- \nSelect and explain. \nA. Mitochondrial DNA mutation, B. Frameshift mutation, C. Y linked disorder, D. Trinucleotide repeat mutation', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Trinucleotide repeat disorders (also known as trinucleotide repeat expansion disorders, triplet repeat expansion disorders or codon reiteration disorders) are a set of genetic disorders caused by trinucleotide repeat expansion, a kind of mutation where trinucleotide repeats in ceain genes exceed the normal, stable threshold, which differs per gene. The mutation is a subset of unstable microsatellite repeats that occur throughout all genomic sequences. If the repeat is present in a healthy gene, a dynamic mutation may increase the repeat count and result in a defective gene.', 'role': 'assistant'}]