Which of the following DNA polymerase enzymes is responsible for filling in the gap during DNA repair mechanisms such as excision repair and mismatch repair?
The correct answer and explanation is:
The DNA polymerase enzyme responsible for filling in the gap during DNA repair mechanisms, such as excision repair and mismatch repair, is DNA polymerase I in prokaryotes and DNA polymerase δ and DNA polymerase ε in eukaryotes.
Explanation:
DNA repair mechanisms are crucial for maintaining the integrity of genetic material by correcting errors or damage that might occur due to external factors like radiation or internal factors like DNA replication errors. Two common types of DNA repair mechanisms are excision repair and mismatch repair.
- Excision Repair:
In excision repair, the DNA damage is recognized, and the damaged portion of the strand is excised. The gap left by the excised segment is then filled by DNA polymerase. In prokaryotic cells, DNA polymerase I is the main enzyme responsible for this task. It has the ability to remove the RNA primer and replace it with the correct nucleotides, filling the gap. In eukaryotic cells, DNA polymerase δ and ε are responsible for filling in these gaps after excision. - Mismatch Repair:
Mismatch repair occurs when DNA polymerase erroneously incorporates an incorrect nucleotide during replication. In both prokaryotic and eukaryotic cells, the mismatch repair system detects these errors. The damaged segment is then excised, and the gap is filled in by the appropriate polymerase. In prokaryotes, DNA polymerase III is mainly responsible for the replication, while DNA polymerase I comes in to replace the incorrect base during repair. In eukaryotes, DNA polymerase δ and DNA polymerase ε are involved in filling in the gap during mismatch repair.
In summary, DNA polymerase I in prokaryotes and DNA polymerase δ and ε in eukaryotes are the key players in filling in the gap during DNA repair mechanisms like excision and mismatch repair. They help ensure that the newly synthesized strand matches the correct DNA sequence and maintain genetic stability.