A researcher isolates DNA from a tissue sample undergoing programmed cell death. When the DNA is run on an agarose gel, a characteristic ladder pattern is observed. Which enzymatic activity is directly responsible for this pattern?
- A Myeloperoxidase
- B Lipoxygenase
- C Caspase-activated DNase (CAD) ✓
- D Xanthine oxidase
Correct answer: C. Caspase-activated DNase (CAD)
Explanation
During apoptosis, caspase-activated DNase (CAD) cleaves nuclear DNA at internucleosomal linker regions, producing fragments in multiples of 180-200 base pairs. This creates the characteristic DNA ladder on gel electrophoresis. Lipoxygenase is involved in leukotriene synthesis. Myeloperoxidase generates hypochlorous acid in neutrophils. Xanthine oxidase generates superoxide during ischemia-reperfusion injury.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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