AQA GCSE Biology

Revision Notes

6.1.8 Sex Determination

Human Chromosomes

  • Ordinary human body cells contain 23 pairs of chromosomes
  • 22 pairs control characteristics only, but one of the pairs carries the genes that determine sex
  • In females, the sex chromosomes are the same (XX)
  • In males, the sex chromosomes are different (XY)


Sex chromosomes, IGCSE & GCSE Biology revision notes

Sperm cells determine the sex of offspring

Determining Sex

  • The inheritance of gender can be shown using a genetic diagram (known as a Punnett square), with the X and Y chromosomes taking the place of the alleles usually written in the boxes


Inheritance of sex, IGCSE & GCSE Biology revision notes

Punnett square showing the inheritance of gender

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