Final answer:
The father determines the sex of the child because he can contribute either an X chromosome, resulting in a female (XX), or a Y chromosome, resulting in a male (XY), which makes him essential in the process of sex determination.
Step-by-step explanation:
The dad determines the sex of the child because he contributes either an X chromosome or a Y chromosome. Each parent contributes one sex chromosome to their child. Mothers can only pass on an X chromosome because they have two X chromosomes (XX). Fathers, on the other hand, can pass on either an X or a Y chromosome because they have one of each (XY). If a father passes on an X chromosome, the child will be female (XX). If the father passes on a Y chromosome, the child will be male (XY). Therefore, the correct answer to the question is B) Because the dad contributes the Y chromosome.
Sex-linked inheritance is crucial in determining the sex of a baby, which is indicated by the presence of sex chromosomes, XX in females and XY in males. The SRY gene on the Y chromosome is essential for triggering the embryonic development of male characteristics. Without the Y chromosome, the embryo develops into a female, considering female as the default sex. Hence, the male parent's contribution is vital in sex determination because the sperm can carry either an X or Y chromosome, whereas the egg from the female parent will always contribute an X chromosome.