GCSEBiology: Combined ScienceAQARevision Notes6. Inheritance, Variation & Evolution6.1 Reproduction6.1.8 Sex Determination

Sex Determination (AQA GCSE Biology: Combined Science)

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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

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Determining Sex

  • The inheritance of sex 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 sex

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    Lára

    Author: Lára

    Expertise: Biology Lead

    Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.