Question:
A patient develops skin cancer and worsening hyperpigmentation following sun exposure. Which DNA repair pathway is most likely impaired?
A patient develops skin cancer and worsening hyperpigmentation following sun exposure. Which DNA repair pathway is most likely impaired?
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UV-induced thymine dimers are repaired by nucleotide excision repair. Defect causes xeroderma pigmentosum.
Updated On: May 14, 2026
- Nucleotide excision repair
- Base excision repair
- Non-homologous end joining (NHEJ)
- Mismatch repair
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The Correct Option is A
Solution and Explanation
Concept:
Ultraviolet radiation causes pyrimidine dimers in DNA. These are repaired by nucleotide excision repair.
Step 1: Identify clinical clue.
Skin cancer and hyperpigmentation after sun exposure suggest defective UV damage repair.
Step 2: Recall UV-induced lesion.
UV light causes: \[ \text{Thymine dimers} \]
Step 3: Recall repair mechanism.
Thymine dimers are repaired by: \[ \text{Nucleotide excision repair} \]
Step 1: Identify clinical clue.
Skin cancer and hyperpigmentation after sun exposure suggest defective UV damage repair.
Step 2: Recall UV-induced lesion.
UV light causes: \[ \text{Thymine dimers} \]
Step 3: Recall repair mechanism.
Thymine dimers are repaired by: \[ \text{Nucleotide excision repair} \]
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