Question

DNA Polymerases Control the Fidelity of Replication

DNA polymerases often have a 3′-5′ exonuclease activity. (All bacterial DNA polymerases have it.)
It is used to excise incorrectly paired bases. (mismatched pairs)

The fidelity of replication is improved by proofreading by a factor of ∼100. (~100-~500)
(Note: this just an average.)
all bacterial polymerases have the ability to ____ but only one can ____ ___

Answer 1

All bacterial DNA polymerases can proofread to ensure replication fidelity, but only DNA polymerase I has the 5'→3' exonuclease activity for RNA primer removal.

Step-by-step explanation:

All bacterial DNA polymerases have the ability to edit DNA by proofreading every newly added base during replication, which allows for a high fidelity of DNA synthesis. However, among the bacterial DNA polymerases, only DNA polymerase I has the additional function of possessing a 5'→3' exonuclease activity, used for removing RNA primers at the terminal ends of DNA fragments.

DNA polymerase III is the primary enzyme for DNA synthesis, while DNA polymerase I and DNA polymerase II are involved mainly in repair. DNA polymerase I is unique in that it has a Klenow fragment with polymerization and proofreading activity but also the mentioned 5'→3' exonuclease function. Proofreading improves replication fidelity considerably by removing incorrect nucleotides that have been inserted and replacing them with the correct ones before DNA synthesis proceeds.