This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Cation used in PCR is 
Select and explain. 
A. Calcium, B. Lithium, C. Magnesium, D. Sodium
C: Magnesium
Answer: C: Magnesium 
Explanation: All polymerases require divalent cations for their activity but some tend to function in buffers containing Mn2+ as well, although a little less efficiently.dNTPs and oligonucleotides bind to Mg2+ and therefore its concentration should exceed the molar concentration of phosphate groups that are contributed from both the dNTPs and primers.dNTPs bind in equimolar concentration with Mg2+.