Final answer:
Chorionic villus cells are genetically identical to the embryo’s mesenchymal cells, as the chorion and its villi are fetal tissues that connect to the mother's blood supply but are genetically part of the fetus.
Step-by-step explanation:
Chorionic villus cells are genetically identical to the embryo's mesenchymal cells. The chorion is a membrane that develops from the syncytiotrophoblast, cytotrophoblast, and mesoderm; it surrounds the embryo and forms the fetal portion of the placenta through the chorionic villi.
The chorionic villi are finger-like projections that burrow into the endometrium, connecting the developing embryo to the mother's blood supply but remain genetically part of the fetus. Therefore, they share the same genetic material as the embryo, including the mesenchymal cells from which they are derived.