AAT Bioquest

What happens if I add too little MgCI2 in my PCR reaction?

Posted April 27, 2023


Magnesium ions are an essential cofactor for polymerase enzyme activity during PCR. They are added in the form of MgCl2 (magnesium chloride). 

When you add too little MgCl2, primers are unable to base pair with the DNA template. This may lead to weak amplification or total PCR failure. 

1.5 to 4.5 mM is the ideal concentration range of MgCl2 in PCR mixtures for satisfactory yield.

Additional resources

Effect of concentration of MgCl2 on random-amplified DNA polymorphism

Polymerase Chain Reaction (PCR)

Helixyte™ Green *20X Aqueous PCR Solution*