Fig. 1.1 shows stages in the development of human twins. [Figure 1.1]

1. (a)On Fig. 1.1, label and name each of the following: • a gamete, • a zygote.[2]
2. (b)Name the part of the female reproductive system that structure P enters.[1]
3. (c)If the sex chromosome in the sperm is a Y chromosome, and in the ovum (egg) is an X chromosome, state the sex of child A and of child B. Explain your answer. child A child B explanation[4]
4. (d)Explain how a woman's body prevents further ova (eggs) from being released until the end of her pregnancy.[4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.