What is the role of DNA polymerase I in bacteria during replication?

• A. It removes RNA primers and fills in with DNA, helping seal Okazaki gaps.
• B. It initiates replication by melting the origin.
• C. It unwinds DNA at the replication fork.
• D. It seals nicks between Okazaki fragments.

Answer: (B)

DNA polymerase I mainly handles primer removal and gap filling during bacterial DNA replication. On the lagging strand, RNA primers laid down by primase must be removed. Pol I uses its 5' to 3' exonuclease activity to remove that RNA primer, then its 5' to 3' polymerase activity to fill the resulting space with DNA. This helps replace RNA with DNA in the Okazaki fragments, moving replication forward. After Pol I updates the primer regions, DNA ligase seals the remaining nicks to create a continuous strand.

So, the best description is that it removes RNA primers and fills in with DNA, aiding in sealing Okazaki gaps. The other roles are performed by different enzymes: initiation of replication by DnaA, unwinding at the fork by helicase, and sealing nicks by DNA ligase.