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This lesson covers how biological sex is determined in humans by the sex chromosomes (XX and XY), as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the role of the sex chromosomes, use a Punnett square to predict the sex of offspring and understand the probability of having a boy or a girl.
Human body cells contain 46 chromosomes arranged in 23 pairs. Of these 23 pairs:
| Sex | Chromosomes | Gametes produced |
|---|---|---|
| Female | XX | All eggs carry an X chromosome |
| Male | XY | Sperm carry either an X or a Y chromosome |
Key points:
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