Explanation:

Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg: True. Mitochondrial replacement therapy (MRT) is an advanced procedure in which the nucleus from an egg or zygote with unhealthy mitochondria is transferred to a donor egg or zygote with healthy mitochondria, from which the nucleus has been removed. The aim is to prevent the transmission of mitochondrial diseases from mother to child.

A child inherits mitochondrial diseases entirely from mother and not from father: True. Mitochondria have their own DNA, which is distinct from the nuclear DNA. Mitochondrial DNA is passed exclusively from mother to child, as the mitochondria in sperm are typically destroyed after fertilization. Thus, mitochondrial diseases are maternally inherited.

Given the explanations above, both statements are correct.