This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2020, Subject name: Pathology
APAF-1 is involved in the activation of which of the following casapses? 
Select and explain. 
A. Caspase 8, B. Caspase 9, C. Caspase 3, D. Caspase 10
B: Caspase 9
Answer: B: Caspase 9 
Explanation: Cytochrome c is released from mitochondria during apoptosis. Once released into the cytosol, cytochrome c binds to a protein called APAF-1 (apoptosis-activating factor-1), forming a multimeric structure called the apoptosome. This complex binds to caspase-9, the critical initiator caspase of the mitochondrial pathway, and promotes its autocatalytic cleavage, generating catalytically active forms of the enzyme.