Question

Mismatch repair mechanism in DNA deals with

• A. Deamination
• B. Adducts and cross-links
• C. Double stranded breaks
• D. Replication errors

Hint:

• Mismatch Repair (MMR) Corrects base-base mismatches and small insertions/deletions that arise during DNA replication and escape the proofreading activity of DNA polymerase.
• Base Excision Repair (BER) Repairs damage to single bases (e.g., deamination, oxidation, alkylation).
• Nucleotide Excision Repair (NER) Repairs bulky lesions that distort the DNA helix (e.g., pyrimidine dimers caused by UV, large chemical adducts).
• Double-Strand Break Repair (DSBR) Homologous Recombination (HR) and Non-Homologous End Joining (NHEJ).

Answer 1

The Correct Option is D

The mismatch repair mechanism in DNA is primarily responsible for correcting replication errors. During DNA replication, the DNA polymerase enzyme can sometimes incorporate incorrect nucleotides. These errors, known as mismatches, can lead to mutations if not corrected. The mismatch repair system identifies and repairs these mismatches to maintain genomic stability and fidelity.

Why Other Options Are Not Correct:

• Deamination: This involves the removal of an amino group from a nucleotide, which often leads to base substitutions. It is generally repaired by the base excision repair pathway, not mismatch repair.
• Adducts and cross-links: These are typically caused by external agents such as chemicals and radiation, leading to modifications in the DNA structure. DNA adducts and cross-links are usually repaired by nucleotide excision repair and other specific repair mechanisms.
• Double stranded breaks: These breaks in the DNA can result from radiation or other external factors and require specialized repair mechanisms like homologous recombination or non-homologous end joining, not mismatch repair.

The replication errors option correctly associates mismatch repair with its primary function of correcting mistakes made during DNA synthesis.