Physiologically, Mg 2+ ions are the most probable co-factors due to their higher concentration in the cells, but sometimes, other ions can also come in. Different ions can affect DNA pols in different ways such as changing the ground state binding affinity of incoming nucleotide , decreasing base selectivity by promoting misincorporation , as well as decreasing base excision rate 10 , among others. Various studies on different polymerases incorporating different ions have shown reduced DNA replication fidelity, as well as mutagenic and carcinogenic properties of ions other than Mg .