Think about the problem here. The most incompatible mitochondria will tend to leak the most free radicals, and so make more copies of themselves. That can have one of two effects. Either the cell dies by apoptosis, removing its load of mitochondrial mutations, or it doesn’t. Let’s consider what happens if the cell dies first. Either it’s replaced, or it isn’t. If it is replaced, all is well. But if it’s not replaced, for example in brain or heart muscle, then the tissue will slowly lose mass.
