Name one DNA repair pathway and its purpose.

Name one DNA repair pathway and its purpose.

• A. Nucleotide excision repair (NER) removes bulky lesions.
• B. Base excision repair (BER) fixes mismatched bases.
• C. Mismatch repair (MMR) replicates damaged DNA to a sister chromatid.
• D. Homologous recombination directly ligates double-strand breaks without a template.

Answer: (A)

Bulky lesions that distort the DNA helix, such as those caused by UV exposure, are exactly the type of damage nucleotide excision repair is built to fix. This pathway recognizes the distortion, makes two incisions around the damaged segment, and removes a short patch of DNA containing the lesion. The gap is then filled in by DNA polymerase using the undamaged strand as a template and sealed by DNA ligase. This direct removal and replacement of the damaged DNA restores the original sequence, which is why this pathway is the correct choice for naming one repair mechanism and its purpose. For context, base excision repair handles small, non-helix-distorting base modifications; mismatch repair fixes errors that slip in during DNA replication; and homologous recombination repairs double-strand breaks using a homologous template, not by ligating ends without a template.

Bulky lesions that distort the DNA helix, such as those caused by UV exposure, are exactly the type of damage nucleotide excision repair is built to fix. This pathway recognizes the distortion, makes two incisions around the damaged segment, and removes a short patch of DNA containing the lesion. The gap is then filled in by DNA polymerase using the undamaged strand as a template and sealed by DNA ligase. This direct removal and replacement of the damaged DNA restores the original sequence, which is why this pathway is the correct choice for naming one repair mechanism and its purpose.

For context, base excision repair handles small, non-helix-distorting base modifications; mismatch repair fixes errors that slip in during DNA replication; and homologous recombination repairs double-strand breaks using a homologous template, not by ligating ends without a template.