Cell cycle and apoptosis · USMLE Step 1

Which of the following is a hallmark biochemical event during the execution phase of apoptosis?

  1. Activation of cyclin-dependent kinases
  2. Phosphorylation of the Rb tumor-suppressor protein
  3. Caspase activation cleaving proteins such as lamins and PARP
  4. A marked increase in the rate of DNA replication
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Correct answer: Caspase activation cleaving proteins such as lamins and PARP

Caspases, a family of cysteine proteases, are activated during apoptosis, cleaving key structural and regulatory proteins (such as nuclear lamins and PARP), resulting in the morphological and biochemical changes characteristic of apoptotic cell death.

Difficulty: Medium Question 10 of 19

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