Q1. [1] § 8.2.4 Sex Determination
Sex is determined by different factors in various species. However, in human beings, it is determined genetically. Which amongst the following option(s) is/are correct for human beings ?
(i) Gamete carrying X chromosome from female parent.
(ii) Gamete carrying X chromosome from male parent.
(iii) Gamete carrying Y chromosome from male parent.
- A (ii) and (iii)
- B (i) only
- C (i) and (iii)
- D (iii) only
Previously asked in CBSE board exam
2026 31/1/1 Q6
Generated by claude-sonnet-4-6 · 2026-06-15 06:51 · grounding rag
Model Answer
Answer: A — (ii) and (iii)
In human beings, females are XX and males are XY. The female parent always gives an X chromosome to all children. The male parent gives either X (producing a girl) or Y (producing a boy) through his gametes. So statements (ii) and (iii) are correct — it is the father's gamete (carrying X or Y) that determines sex, not the mother's.
Source: Chapter 8, Section 8.2.4 – Sex Determination
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Explanation
- Statement (i) is incorrect because the female (mother) always contributes an X chromosome — this does not determine sex, as it is constant.
- Statements (ii) and (iii) are correct because the male contributes either X or Y, making sex determination entirely dependent on the paternal gamete.
- Key exam point: Sex is determined by the father, not the mother in human beings.
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