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
In Downs syndrome there is? 
Select and explain. 
A. Translocation, B. Mutations, C. Paternal nondisjunction, D. Maternal nondisjunction
D: Maternal nondisjunction
Answer: D: Maternal nondisjunction 
Explanation: Ans. (d) Maternal nondisjunction(Ref: R 9th/pg 161)Down's syndrome is most commonly caused by Maternal nondisjunction Q > Translocation > Mosaicism