Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
Well-adjusted barometer can help you predict changing weather day to day because it detects minute changes in the air pressure.
D. In a structure of the female reproductive system.
