Christianity: The Spirit created it by an effortless, touchless, omnipotent act. “That which is conceived in her is from the Holy Spirit.” (Matthew 1:20; cf. Luke 1:35) 100% of the DNA was mortal, and none of the DNA was transferred from any divine being.
20th century Mormonism: Heavenly Father (Adam’s spirit father) did via natural action. “He was begotten, conceived and born in the normal and natural course of events, for he is the Son of God, and that designation means what it says.” (Bruce McConkie, Mormon Doctrine, 1966, p. 742)
Brigham Young’s 19th century Mormonism: Adam, the Heavenly Father of our spirits, did. “Jesus, our elder brother, was begotten in the flesh by the same character that was in the garden of Eden, and who is our Father in Heaven.” (Journal of Discourses 1:50, 51)
One Mormon naturalistically argues:
“If the birth [of Jesus] had been truly virgin, then Jesus would have been female, as parthenogenesis invariably must result in female offspring, since there’s no Y chromosome available to make it otherwise.”
(accessed December 17, 2010, domain since removed)
But if God was able to create the Y-chromosome from scratch (or at least from non-bodily materials) for Adam, why not with the Second Adam, Jesus Christ? As the angel to Mary explained John’s conception in Elizabeth: “For nothing will be impossible with God.” (Luke 1:37)