The Catholic Church condemned the heresy of Valentinus who wrongly taught that Jesus did not take genetic material from Mary, but rather passed through her “like water through a straw.”
We also know from Catholic Teaching that Jesus is a Divine Person with two separate natures; one divine and one human. Jesus, a divine Person with a divine nature is co-equal to the Father, yet acquired His genetic human material from Mary. Normally, a child’s DNA must come from a mother (XX chromosomes) and a father (XY chromosomes). How is it possible that Jesus received all His DNA from just Mary?
The question is similar to Mary’s own question to Gabriel: “How can this be, since I have no relations with a man?” The answer also is similar to the answer that Gabriel gave Mary: “The Holy Spirit will come upon you, and the power of the Most High will overshadow you . . . for nothing will be impossible for God“.
It would seem then that the overshadowing of the Holy Spirit involved adding the genetic Y chromosome needed for Jesus to be a male. As Saint Thomas Aquinas says, Mary cannot be both the Mother and Father of Jesus. However this does NOT mean that the Holy Spirit is the Father of Christ.
Mary is the woman chosen from all women to put flesh and bones on the Son of God – to give Him the color of His eyes and His hair. She was to teach Him how to talk and she was to help baby Jesus take His first baby steps. Mary was the one chosen to give Him the Body and Blood in which He would live, suffer and die to redeem us.
Sometimes we ask, will a child look like its mother or its father? In this case – there was no such question. Jesus was the Divine image and likeness of His Father and He was the human image and likeness of His Mother. Mary was the sole biological parent of Jesus, while Saint Joseph was His foster-father. By the power of the Holy Spirit, Mary alone furnished the Sacred Body of her Son.
Just as Jesus, as the Divine Son, was eternally begotten from the substance of the Father; so Jesus, as the Son of Man, was conceived and born from the flesh and blood of Mary His mother.