This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Single Gene Disorders, Subject name: Pathology
[{'content': 'Increasing severity of mental retardation in 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: Anticipation Increasing severity of disease in successive generations Trinucleotide repeats cause worsening of clinical features with each successive generation.', 'role': 'assistant'}]