Final answer:
The risk of Jack and Sally's child inheriting Jack's mitochondrial disease is 0% as such diseases are usually passed through the mother, and Sally does not have the disease.
Step-by-step explanation:
The risk that Jack and Sally's child will have the mitochondrial disease that Jack has been diagnosed with is generally considered to be 0%. This is because mitochondrial diseases are typically inherited through the maternal line, since mitochondria are passed from mother to child through the egg cell. The father's sperm does not contribute mitochondria to the embryo. Therefore, if Sally does not have the disease and hence does not have affected mitochondria, their child is not expected to inherit the disease from Jack.