Mg²⁺ in PCR acts as
Divalent magnesium ions serve as an essential cofactor for DNA polymerases in PCR. Mg2+ coordinates with phosphate oxygens of dNTPs at the active site, facilitates nucleophilic attack by 3' hydroxyl, stabilizes negative charges during phosphodiester bond formation, and influences primer-template duplex stability. Concentration critically affects enzyme activity, fidelity, specificity, and primer annealing. Unlike an enzyme that catalyzes reaction itself, buffer that maintains pH, or template that encodes sequence, Mg2+ is a non-protein chemical activator indispensable for catalytic function an
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
