Question

Humans have 23 pairs of chromosome in every body cell. Even one extra chromosome causes death or serious disorders. For example, an extra copy of chromosome 21 causes Down syndrome. Which of the following are affected in a human being with an extra chromosome? Choose the 3 items that apply.

Answer 1

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.