Question

Consider the following statements:
(i) The sex of a child is determined by what it inherits from the mother.
(ii) The sex of a child is determined by what it inherits from the father.
(iii) The probability of having a male child is more than that of a female child.
(iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote.
The correct statements are:

• A. (i) and (iii)
• B. (ii) and (iv)
• C. (iii) and (iv)
• D. (i), (iii) and (iv)

Answer 1

The Correct Option is B

Step 1: Understanding how the sex of a child is determined:
The sex of a child is determined by the combination of sex chromosomes inherited from the parents.
Humans have two sex chromosomes: X and Y. Females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
The mother always passes an X chromosome, while the father passes either an X or a Y chromosome.

Step 2: Analyzing the given statements:
(i) The sex of a child is determined by what it inherits from the mother:
This statement is incorrect. The mother only passes an X chromosome, but the sex of the child is determined by whether the father contributes an X or a Y chromosome.

(ii) The sex of a child is determined by what it inherits from the father:
This statement is correct. The father determines the sex of the child by passing either an X or a Y chromosome. If the father passes an X chromosome, the child will be female (XX). If the father passes a Y chromosome, the child will be male (XY).

(iii) The probability of having a male child is more than that of a female child:
This statement is incorrect. The probability of having a male or female child is equal, as the father has a 50% chance of passing either an X or a Y chromosome.

(iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote:
This statement is correct. The fusion of the male (sperm) and female (egg) gametes during fertilisation determines the sex of the child, depending on whether the sperm carries an X or Y chromosome.

Conclusion:
The correct statements are (ii) and (iv). Therefore, the correct answer is (ii) and (iv).