The human gametes contain 23 chromosones each, when combined they make the full 46 that humans have. It is the position of the Church that the entirety of Jesus' humanity is derived from Mary.
Exactly how this happened is not clear, whether God created an embryo that utilized her genetic material, or whether He created the necessary male components to fertilize her ovum. That is not something that we can ever know.
What we do know is that Jesus had only one human parent, Mary. As you see your own children and how they resemble their parents or grandparents or others in the family, Jesus would have only had such familial resemblance to Mary's family.
SD