In base excision repair (BER), which enzyme initiates the repair process by recognizing and removing a damaged or inappropriate base, creating an abasic (AP) site?

• A DNA glycosylase ✓
• B AP endonuclease
• C DNA polymerase β
• D DNA ligase

Explanation

DNA glycosylase initiates base excision repair by cleaving the N-glycosidic bond between the damaged base and the sugar-phosphate backbone, creating an abasic site. AP endonuclease then nicks the backbone at this site. DNA polymerase β inserts the correct nucleotide, and DNA ligase seals the nick. The most tempting distractor is AP endonuclease, which acts after glycosylase has already removed the base.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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