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': 'Most common cause of Down syndrome is \nSelect and explain. \nA. Robesonian translocation, B. Mosaicism, C. Meiotic nondisjuction, D. Epigenetic mutation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Genetics of Down syndrome 95% cases - Meiotic nondisjunction of chromosome 21 occurring in the ovum 4% cases - Robesonian translocation 1% cases - Mosaicism resulting from mitotic nondisjunction of chr 21', 'role': 'assistant'}]