I’m afraid you are mixing up two things. In a plain old regular human, male and female DNA meet up in the sperm and egg.
Mitochondrial DNA is entirely different. A mitochondria is a little powerhouse that lives in every one of your cells. Unlike your regular DNA, it isn’t as good at repairing itself. From recent research on mice, it appears that the damage the Mitochondria endures over time is one reason we age over time.
Mitochondrial DNA is often called the “Eve gene” because it is always inherited from the mother. In a regular human, the sperm is a small cell and uses every bit of it’s energy to get to the egg. The sperm’s (and thus, the male’s) mitochondria then withers and dies. The egg, on the other hand, is a very large cell with the capability to pass on, not just it’s share of the female’s genetics, (regular DNA) but also the mitochondrial DNA.
In the case of Jesus, only His Mother contributed DNA (from David’s line). The Holy Spirit would have provided something compatible. We, of course, have no idea what form that would take. His mitochondrial DNA would have come from Mary, under normal circumstances. Since He did age, I suppose that would be a reasonable theory.