Which enzyme removes RNA primers and replaces them with DNA during replication?

Which enzyme removes RNA primers and replaces them with DNA during replication?

• A. DNA polymerase II
• B. DNA ligase
• C. RNAse H
• D. DNA polymerase I

Answer: (D)

RNA primers laid down during replication must be removed and replaced with DNA. The enzyme that does this in the classic bacterial replication model has two functions: it uses 5' to 3' exonuclease activity to remove the RNA primer and then switches to 5' to 3' polymerase activity to synthesize DNA in that gap. After this replacement, DNA ligase seals the remaining nick between adjacent DNA fragments. Other enzymes either only remove RNA or only seal nicks, or are mainly involved in repair, so they don’t accomplish both primer removal and DNA replacement. DNA polymerase I is the one that performs both steps.

RNA primers laid down during replication must be removed and replaced with DNA. The enzyme that does this in the classic bacterial replication model has two functions: it uses 5' to 3' exonuclease activity to remove the RNA primer and then switches to 5' to 3' polymerase activity to synthesize DNA in that gap. After this replacement, DNA ligase seals the remaining nick between adjacent DNA fragments. Other enzymes either only remove RNA or only seal nicks, or are mainly involved in repair, so they don’t accomplish both primer removal and DNA replacement. DNA polymerase I is the one that performs both steps.