God says in Gen 3 that the one who will crush the serpents head is the seed of the woman.
My reasoning on why Jesus could get his human nature and flesh from Mary and not inherit a nature to sin, is from God's declaration of federal headship in the man, not the woman. It is a decree. Therefore, even though women are just as sinful as men, by decree of God, that nature of Adam comes from the male, and that is how the children are born sinners---including their mothers. Both genders have sin nature, but a child conceived of the Holy Spirit does not have a human father.
That is the only difference I am able to see. I think if frankly useless to speculate on how that came to be or how the sin nature is passed from the father---such as DNA or genetics or what not. Or whether or not God used an ovum from Mary. Or any other speculation. We don't know and we don't have to know everything. We are grossly kidding ourselves if we think we can figure it all out. That is just my two cents. I know many find the topic fascinating, and enjoy the discussions on it. I am not giving a lecture.
One thing though, I have now heard three solid Bible students on the forum say that Jesus was created. I am shocked! That is so against orthodoxy that I don't know where it came from. I have been a Christian for over forty years and today was the first time I ever heard a Trinitarian say or write that, and I heard it from three different people. What is going on?