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 sex determination:
A child's sex is determined by the sex chromosomes inherited from parents. Humans have X and Y chromosomes. Females are typically XX, and males are XY. The mother always contributes an X chromosome, while the father contributes either an X or a Y chromosome.

Step 2: Analyzing statements:
(i) Child's sex is determined by maternal inheritance:
Incorrect. The mother only provides an X chromosome. The father's contribution (X or Y) determines the child's sex.

(ii) Child's sex is determined by paternal inheritance:
Correct. The father determines the sex by providing an X or Y chromosome. An X from the father results in a female (XX), and a Y results in a male (XY).

(iii) Probability of male child is higher than female child:
Incorrect. The probabilities are equal because the father has a 50% chance of passing an X or a Y chromosome.

(iv) Sex is determined at fertilization by gamete fusion:
Correct. The fusion of male (sperm) and female (egg) gametes during fertilization establishes the sex based on whether the sperm carries an X or Y chromosome.

Conclusion:
Correct statements are (ii) and (iv). The correct answer is (ii) and (iv).