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

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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