Final answer:
The Bcl-2 protein prevents apoptosis by inhibiting the release of cytochrome C. Cladribine is an example of a molecule that can block or inactivate Bcl-2, allowing apoptosis to proceed.
Step-by-step explanation:
The Bcl-2 protein is a key regulator of apoptosis, or programmed cell death. Bcl-2 prevents apoptosis by inhibiting the release of cytochrome C from the mitochondria, which is necessary for the activation of caspases and the initiation of apoptosis. However, there are certain molecules that can block or inactivate Bcl-2, allowing the BH123 pathway to continue towards apoptosis. One example of a molecule that can block or inactivate Bcl-2 is a deoxyadenosine analog called cladribine.