Understanding Recombination Repair: Identifying the Incorrect Statement

Recombination repair is a vital DNA repair process that rectifies damaged DNA, especially when both strands are affected or when gaps are left opposite lesions during replication. It utilizes homologous sequences to accurately restore DNA integrity, ensuring genomic stability.

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Evaluating the Statements About Recombination Repair

1. DNA polymerase III stalls at the site of the damage.

   • This is correct. During replication, DNA polymerase III encounters lesions like thymine dimers and stalls because it cannot incorporate nucleotides opposite damaged bases.

2. DNA polymerase III leaves a gap in the daughter strand.

   • This is correct. To bypass the lesion, DNA polymerase III skips the damaged site, leaving a single-stranded gap in the newly synthesized daughter strand.

3. The gap is filled by recombination between complementary parent strand homologous to daughter strand and the gapped daughter strand.

   • This is correct. The gap is repaired by homologous recombination, using the undamaged complementary parental strand as a template to fill in the missing sequence.

4. Homologous recombination process is catalyzed by topoisomerase II.

   • This is incorrect. Homologous recombination is catalyzed primarily by recombinase proteins such as RecA in prokaryotes and Rad51 in eukaryotes. Topoisomerase II is involved in managing DNA topology (e.g., relieving supercoiling during replication and transcription) but does not catalyze homologous recombination.

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Summary Table

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Keywords for SEO Optimization

• Recombination repair mechanism

• DNA polymerase III stalling

• DNA gap repair by homologous recombination

• Role of RecA and Rad51 in recombination

• Topoisomerase II function in DNA metabolism

• DNA damage bypass and repair

• Homologous recombination proteins

• DNA replication fork stalling

• Post-replication repair

• DNA strand invasion and repair synthesis

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Conclusion

In recombination repair, DNA polymerase III stalls at DNA damage sites and leaves gaps in the daughter strand. These gaps are accurately repaired by homologous recombination using the complementary parental strand as a template. However, the statement that homologous recombination is catalyzed by topoisomerase II is incorrect. Instead, recombinase proteins like RecA and Rad51 mediate this process.

Correct answer: (4) Homologous recombination process is catalyzed by topoisomerase II is the incorrect statement.