Ladder pattern of DNA electrophoresis in apoptosis is caused by the action of the following enzyme
**Core Concept**
The ladder pattern observed in DNA electrophoresis during apoptosis is a hallmark of programmed cell death. This phenomenon is caused by the fragmentation of DNA into internucleosomal fragments, which results in a characteristic ladder-like pattern. The enzyme responsible for this DNA fragmentation is a key player in the apoptotic process.
**Why the Correct Answer is Right**
During apoptosis, the enzyme caspase-activated deoxyribonuclease (CAD) is activated, leading to the cleavage of DNA at internucleosomal sites. This results in the formation of a ladder pattern in DNA electrophoresis, with fragments of 180-200 base pairs (bp) separated by approximately 10-15 bp. The activation of CAD is mediated by caspase-3, which is a key executioner caspase in the apoptotic pathway. The cleavage of DNA by CAD is a crucial step in the apoptotic process, allowing the cell to undergo a controlled form of cell death.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the enzyme responsible for DNA fragmentation in apoptosis is CAD, not DNase I. While DNase I is a nuclease involved in DNA degradation, it is not the primary enzyme responsible for the ladder pattern observed in apoptosis.
**Option B:** This option is incorrect because the enzyme caspase-1 is involved in the activation of inflammatory processes and is not directly responsible for DNA fragmentation in apoptosis.
**Option C:** This option is incorrect because the enzyme caspase-8 is involved in the initiation of apoptosis, but it is not directly responsible for the DNA fragmentation observed in apoptosis.
**Clinical Pearl / High-Yield Fact**
The ladder pattern of DNA electrophoresis in apoptosis is a critical diagnostic feature of programmed cell death, and it can be used to distinguish apoptosis from necrosis, which is characterized by random DNA fragmentation.
**Correct Answer: C. Caspase-activated deoxyribonuclease (CAD)**