Draw a flow chart to show that sex is determined genetically in human beings.
Generated by claude-sonnet-4-6 · 2026-06-15 06:54 · grounding rag
Model Answer
Flow chart: Sex Determination in Human Beings
```
Parents: Father (44 + XY) × Mother (44 + XX)
↓ ↓
Gametes: 50% sperm with X All eggs with X
50% sperm with Y
↓
Fertilisation
↓
┌────────────────┴────────────────┐
Egg (X) + Sperm (X) Egg (X) + Sperm (Y)
↓ ↓
Child = XX Child = XY
(Girl) (Boy)
```
- All children inherit X chromosome from mother.
- Sex is determined by the chromosome inherited from the father.
- Father's X → Girl; Father's Y → Boy.
- Half the children will be boys and half will be girls.
Source: Chapter 8, Section 8.2.4 – Sex Determination
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Explanation
- Examiners expect a clearly labelled flow chart showing parents → gametes → fertilisation → offspring. Draw it neatly in the exam.
- Key point to state: mother always contributes X; the father's contribution (X or Y) determines the sex.
- Mention the 44 autosomes + sex chromosomes notation for full marks.
- The conclusion — 50% boys, 50% girls — must appear either in the chart or as a point below it.