This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Best sample for DNA karyotyping ? 
Select and explain. 
A. Blood, B. Bone marrow, C. Amniotic fluid, D. Chorionic villi
A: Blood
Answer: A: Blood 
Explanation: Ans. is 'a' i.e., BloodKaryotyping is the study of number and appearance of chromosomes,Most commonly used sample is blood. Blood is centrifuged. WBCs are separated. White Blood cells are rapidly dividing cells with DNA.