In Escherichia coli, removal of RNA primers from Okazaki fragments during replication is carried out by:
- A DNA polymerase I via its 5' to 3' exonuclease activity ✓
- B DNA polymerase III via its 3' to 5' exonuclease activity
- C DNA ligase via nick sealing
- D Primase via reverse transcription of the primer
Correct answer: A. DNA polymerase I via its 5' to 3' exonuclease activity
Explanation
DNA polymerase I uniquely possesses 5' to 3' exonuclease activity, which degrades the RNA primer ahead of it while its polymerase activity fills the gap with DNA. Ligase then seals the final nick. The 3' to 5' exonuclease of both Pol I and Pol III serves proofreading, not primer removal. Primase synthesizes primers and does not remove them. This division of labor among the three prokaryotic polymerases is a classic examination point.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.