Mat 7:11 "If you then, being evil, know how to give good gifts to your children, how much more will your Father who is in heaven give what is good to those who ask Him!"
You assume a person inherits their genetic makeup from the mother. I would disagree and say the genetic makeup is from the father. In this sense the literal Father. After all the Nicene Creed itself states Christ was "conceived by the Holy Spirit".
Whether it is Mary's "egg" or God miraculously planted the whole thing is inconsequential. Sin is transmitted through the male and Mary was impreganted with perfection. One could possibly say all women eggs are pure and holy. It is the man who is the problem.
That's not in the Bible, Harley. That's Protestant tradition.
(BTW, Catholics and Orthodox believe nothing remotely like it. Original sin is the inherited lack of grace, not some polluted "Adamic nature" that is transmitted from men.)
I do not think it at all wrong to speak of Christ having sinful nature if by that you mean He was (by choice) beset by weaknesses and temptations and ultimately death. The Scriptures state very explicitly that He became sin for us: not, we may be sure, that He Himself sinned, but that He in some manner truly bore our sin, our sinfulness, right down to our death. Christ became a part of fallen human nature; this is the remarkable thing about it. He did not come as some sort of demi-god who never became weary or never had to eat or drink. He was not unnassailable, and in that fact- that He was truly passible and capable of temptation- His victory over Satan was a true one, waged in human flesh like ours.
He shared fully in our broken, worn-out, enslaved human nature, and by doing so He was able to free us from the bondage in which we were kept. He 'became sin' for us, so that we might become the righteousness of God. He willingly took on the corruption of man so that He might rid us of that corruption. He willingly took on the weakness of a human will so that He might correct it and turn it rightly to God.
Christ did not assume a truly perfect, glorified humanity until after the Resurrection: perfect in the sense of completion, not in the sense of not having sinned. Indeed, the book of Hebrews goes so far as to say that Christ was made perfect by learning obedience (as a man like us). He suffered, then He put on glory.
I hope I don't sound to grating on a small point: it is just that I am convinced of the immense importance of these small points, because they, when taken together to help from our understanding of this Man from Nazareth, compose the Great Point of all human existence and meaning.
Also, I hope that we aren't talking past each other to badly. I suspect I mean something different from 'sin nature' than you, which goes back to the Greek/Latin dichotomy noted above. My primary theological influences are more Greek than Latin.