DNA polymerase I of E. coli is involved in the removal of RNA primers from Okazaki fragments. Which enzymatic activity of DNA polymerase I mediates this primer removal?
- A 3' to 5' exonuclease activity
- B 5' to 3' polymerase activity
- C 5' to 3' exonuclease activity ✓
- D Endonuclease activity directed at the RNA-DNA junction
Correct answer: C. 5' to 3' exonuclease activity
Explanation
DNA polymerase I is unique among E. coli polymerases in possessing a 5' to 3' exonuclease activity, which excises the RNA primer nucleotides ahead of the growing DNA strand during nick translation. The 3' to 5' exonuclease activity serves a separate function, proofreading of newly incorporated bases. The 5' to 3' polymerase activity fills the gap left after primer removal but cannot itself degrade RNA.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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