If cytochrome c is injected into normal and mutant cells lacking Bax and Bak, what is the predicted response?

The injection of cytochrome c into cells typically stimulates the apoptosome formation, which is instrumental in initiating the downstream signaling cascade that leads to apoptosis. In normal cells, cytochrome c leads to the activation of initiator caspases, ultimately causing programmed cell death.

In the context of cells lacking both Bax and Bak, which are pro-apoptotic factors crucial for cytochrome c release from the mitochondria, one might initially think these mutant cells would be protected from apoptosis. However, since the question specifies that cytochrome c is injected directly into the cells, this bypasses the need for mitochondrial signaling. The apoptotic pathway can still be triggered in both normal and mutant cells upon introduction of cytochrome c into the cytosol, leading to the activation of caspases and, consequently, apoptosis.

This explains why both normal and mutant cells undergo apoptosis upon injection of cytochrome c, as it provides what is essentially an external signal that directly engages the apoptotic machinery, independent of Bax and Bak function.