This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
The type mutation that leads to replacement of valine for glutamate in sickle cell disease is 
Select and explain. 
A. Point mutation, B. Silent mutation, C. Nonsense mutation, D. Any of above
A: Point mutation
Answer: A: Point mutation 
Explanation: Sickle-cell anemia is caused by apoint mutation in the b-globin chain of hemoglobin, causing the hydrophilic amino acid glutamic acid to be replaced with the hydrophobic amino acid valine at the sixth position. The b-globin gene is found on the sho arm of chromosome 11. Ref ganong's review of medical physiology 25e