Uracil incorporated into DNA by spontaneous deamination of cytosine is removed primarily by which repair pathway?
- A Base excision repair initiated by a specific glycosylase ✓
- B Nucleotide excision repair
- C Mismatch repair using MutS homologs
- D Nonhomologous end joining
Correct answer: A. Base excision repair initiated by a specific glycosylase
Explanation
Base excision repair handles small, non-helix-distorting base lesions. Uracil-DNA glycosylase cleaves the N-glycosidic bond, creating an abasic site that AP endonuclease incises; the gap is filled by polymerase and sealed by ligase. Nucleotide excision repair targets bulky adducts such as pyrimidine dimers, mismatch repair corrects replication errors, and nonhomologous end joining rejoins double-strand breaks. This pathway distinction between small versus bulky lesions is repeatedly examined.
Reference: Lehninger Principles of Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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