Which is activated for nuclear fragmentation in apoptosis?
**Core Concept**
Apoptosis is a programmed cell death process that involves a series of biochemical events leading to the fragmentation of the cell nucleus. This process is crucial for eliminating damaged or unwanted cells in multicellular organisms. The activation of specific enzymes is essential for initiating nuclear fragmentation during apoptosis.
**Why the Correct Answer is Right**
The correct answer is a caspase, specifically caspase-activated deoxyribonuclease (CAD). CAD is a nuclease that is activated by caspase-3 during the late stages of apoptosis. Once activated, CAD cleaves the DNA at internucleosomal linker regions, resulting in the characteristic fragmentation of the cell nucleus. This process is essential for the efficient execution of apoptosis and the maintenance of cellular homeostasis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, although it is involved in apoptosis, it is not directly responsible for nuclear fragmentation.
**Option B:** This option is incorrect because it is a pro-apoptotic protein that is involved in the activation of caspases, but it does not directly participate in nuclear fragmentation.
**Option C:** This option is incorrect because it is involved in the regulation of apoptosis, but it does not play a direct role in the activation of CAD or nuclear fragmentation.
**Clinical Pearl / High-Yield Fact**
It is essential to note that the activation of CAD is a critical step in the execution of apoptosis, and its dysregulation has been implicated in various diseases, including cancer and neurodegenerative disorders.
**Correct Answer: C. CAD**