The Y chromosome is passed from father to son. The Y chromosome is not passed from father to daughter. It is not passed from mothers to their children, because it was not passed from their fathers to them. The mitochondrial, or MtDNA, is passed from the mother to children of both sexes, as it was passed to her from her mother and her mother's mother. It is not passed from fathers to daughters or sons, even though it was passed to the father from his mother.