DNA Polymerases are a family of conserved enzymes that polymerize or extend DNA. While there are different families of polymerases, the structures of known DNA polymerases are highly conserved and the fundamental enzyme activity remains the same. The enzyme catalyzes the addition of monomeric deoxyribonucleoside triphosphates (dNTPs) onto the 3’ hydroxyl end of an existing DNA or RNA primer. This elongation reaction produces extended DNA and inorganic pyrophosphates. DNA polymerase does not have absolute fidelity and is prone to mismatching a base pair at a rate of one per billion base pairs. Thus, certain DNA polymerase families also contain a 3’-5’ exonuclease activity, allowing the polymerase to proofread by moving back one base and excising the error.