In human beings, females have XX chromosomes and males have XY chromosomes. Explain why the sex of a child is determined by the father and not the mother.
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
The mother has only X chromosomes (XX), so she can only pass an X chromosome to her child. The father has XY chromosomes, so he can pass either X or Y. If the father passes X, the child is a girl (XX); if he passes Y, the child is a boy (XY). Thus, the sex of the child is determined by the father.
Source: Chapter 8, Section 8.2.4 – Sex Determination
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Explanation
- The key logic: mother always contributes X, so she cannot determine sex. Only the father's contribution (X or Y) decides the outcome.
- Examiners look for: (1) mother's limitation (only X), (2) father's two possibilities (X or Y), (3) clear conclusion linking Y → boy, X → girl.
- Avoid vague statements — be specific about which chromosome does what.