If egg and sperm form first cell of baby, then why does mtDNA comes from mother only?

Question

If egg and sperm form first cell of baby, then why does mtDNA comes from mother only?

In: Biology

Answer 1

Just like any other cell, the egg contains mitochondria–they’re required for it to make use of energy and divide, which are both quite important functions for an egg! Since the mitochondria are already present in the egg before the sperm gets anywhere near it, they contain only the mother’s DNA. The mitochondria in the sperm, which are far less numerous than the ones in the egg anyway, are destroyed as part of the fertilisation process, nobody is entirely sure why.