Question

The maleness of a child is determined by:

• A. The X chromosome in the zygote
• B. The Y chromosome in the zygote
• C. The cytoplasm of germ cell which determines the sex
• D. Sex is determined by chance

Answer 1

The correct option is B

The Y chromosome in the zygote

The correct option is B.

Explanations of the correct option:

Option B:

1. Male sex character is determined by the Y-chromosome inherited from the male parent.
2. Hence, a male has sex chromosomes X and Y, while a female has XX as sex chromosomes.
3. During fertilization, the mother always contributes an X chromosome while the father either contributes an X or a Y chromosome.
4. Hence, the male character of the child is determined by the Y chromosome in the zygote.
5. Humans have 23 pairs of chromosomes. Out of these 23 pairs, 22 pairs are Autosomes and only one pair is the ‘Sex Chromosome’, which actively takes part in the process of sex determination.
6. The two sets of chromosomes are carried by both the sexes (male and female).
7. Male has one XY set of sex chromosomes in which both are active
8. Female has both X (XX) sex chromosomes in which one is active.
9. The XY sex-determination system is found in humans, mammals, some insects, and a few plant species.
10. All children will inherit an X chromosome from their mother, despite whether they are a boy or girls.
11. Therefore, the male parent helps in the determination of the sex of the child.
12. A child who inherits the Y chromosome will be a boy and one who inherits the X chromosome will be a girl.

Explanations of the incorrect option:

Option A:

The x chromosome does not contribute to maleness.

Option B:

The cytoplasm of germ cells contributes to the maternal effect.

Option C:

Sex is determined by the probability of the set of sex chromosomes from the male and female parent.

Final answer: The maleness of a child is determined by the Y chromosome in the zygote.