The base of an adenine molecule is made of ribose sugar molecules
Involuntary action in body
Answer:
Scientists repeats the steps in cycle mode and in order to be sure about the results he/she chosen.
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.
