A couple is expecting a baby. The mother contributes an X chromosome to the child. Explain how the father's contribution determines whether the child will be a boy or a girl.
Generated by claude-sonnet-4-6 · 2026-06-26 01:03 · grounding rag
Model Answer
The father has two sex chromosomes: X and Y. During reproduction, he can pass either an X or a Y chromosome to the child. Since the mother always contributes an X chromosome, if the father contributes an X chromosome, the child will be a girl (XX). If the father contributes a Y chromosome, the child will be a boy (XY). Thus, the father's contribution determines the sex of the child.
Source: Chapter 8, Section 8.2.4 – Sex Determination
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Explanation
- The examiner wants you to clearly state that the father is either XY and can pass X or Y, while the mother always passes X.
- Mention both outcomes (XX = girl, XY = boy) explicitly — each is worth marks.
- Do not say the mother determines sex; the passage clearly states sex is determined by the paternal chromosome.
- The phrase "father's contribution determines the sex" should appear in your answer to directly address the question.