GCSE Biology (AQA)

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Sex Determination

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Inheritance, Variation and Evolution Reproduction

Sex Determination

1:34 Sex Determination and Inherited Disorders
Spec 4.6.1.8
Previous Genetic Crosses & Probability Next Polydactyly
  • Human body cells have 23 pairs of chromosomes.
  • 22 pairs control various characteristics.
  • The 23rd pair determines sex characteristics, such as having testes or ovaries.
  • Females have XX chromosomes, while males have XY chromosomes.
  • The probability of having a child with XX or XY chromosomes can be demonstrated using a genetic cross.
  • A Punnett square shows that there is a 50% chance for XX and 50% chance for XY, resulting in a 1:1 ratio.
  • This indicates a 50/50 chance of having a genetically male or female baby.
  • Understanding how to perform a genetic cross for X and Y chromosome inheritance is important for exams.

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