Final answer:
During DNA replication, DNA polymerase I and III proofread the new DNA strands, excising incorrectly paired nucleotides with their exonuclease activity and replacing them with the correct ones to maintain genetic fidelity.
Step-by-step explanation:
DNA polymerase I and DNA polymerase III play crucial roles during DNA replication by proofreading to ensure accuracy in the DNA synthesis process. These enzymes possess exonuclease activity that allows them to remove incorrectly paired nucleotides. DNA polymerase III primarily adds new nucleotides to the growing DNA strand and conducts proofreading with its 3' to 5' exonuclease activity. When an incorrect base is detected, it is excised, and the correct nucleotide is added in its place. Additionally, DNA polymerase I also contributes to this fidelity check and is particularly responsible for removing the RNA primer and replacing it with DNA nucleotides, ensuring any resulting gaps are properly sealed with the correct sequence.
Without this crucial proofreading function, the error rate of DNA replication would be much higher, potentially leading to mutations and impaired function of the cell. Thus, the proofreading mechanism is an essential element in maintaining the integrity of the genetic information.