This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Pediatrics
Leiden mutation involves: 
Select and explain. 
A. Factor V, B. Factor VI, C. Protein C, D. Protein S
A: Factor V
Answer: A: Factor V 
Explanation: a. Factor V(Ref: Nelson's 20/e p 2384-2389, Ghai 8/e p 350-352)Factor V Leiden: glutamine arginine substitution at amino acid residue 506 that renders factor V resistant to cleavage and inactivation by protein C (also called Activated Protein C resistance)