Why is it that monozygotic twins share 100% of their genes?
A) Because they are the result of two sperm cells fertilizing the same egg, and thus that egg make sure to choose only the same genes from each of the sperm cells.
B) Because they are the result of one zygote that split in two, making a perfect replica of itself.
C) Because they are the result of two zygotes being formed at precisely the same time.
D) Because they are born at the same time, and thus have the same start to their phenotypical development.

Question

Quizplus · Accepted Answer

Monozygotic twins are formed when one zygote (formed by the fusion of a sperm and egg) splits into two separate embryos. Since they come from the same zygote, they have the exact same genetic material, resulting in a 100% genetic match.

Why Is It That Monozygotic Twins Share 100% of Their