DNA polymerase I is primarily responsible for which action during DNA replication?

DNA polymerase I plays a critical role during DNA replication, particularly in the removal of RNA primers. During the initiation of DNA replication, short RNA primers are synthesized by primase to provide a starting point for DNA synthesis. DNA polymerase III then extends these primers by adding DNA nucleotides. However, once the synthesis of the new DNA strand progresses, the RNA primers need to be removed to ensure that all segments of the new DNA are composed entirely of DNA nucleotides.

DNA polymerase I has a specific function in this process as it possesses exonuclease activity, allowing it to remove the RNA primers one nucleotide at a time. After removing the RNA primers, DNA polymerase I also has the ability to fill in the gaps left behind with DNA nucleotides, ensuring the continuity and integrity of the newly synthesized DNA strand.

In contrast, while DNA polymerase I does add new nucleotides to fill in gaps, its primary responsibility is the removal of RNA primers. Other enzymes, such as helicase, are in charge of unwinding the DNA helix, and DNA ligase is responsible for joining DNA fragments like Okazaki fragments on the lagging strand.