This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Pathology
[{'content': 'In Downs syndrome there is? \nSelect and explain. \nA. Translocation, B. Mutations, C. Paternal nondisjunction, D. Maternal nondisjunction', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. (d) Maternal nondisjunction(Ref: R 9th/pg 161)Down's syndrome is most commonly caused by Maternal nondisjunction Q > Translocation > Mosaicism", 'role': 'assistant'}]