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Sex Determination (AQA GCSE Biology)

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Written by: Lára Marie McIvor

Reviewed by: Lucy Kirkham

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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

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

Last updated: 29 August 2024

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Author: Lára Marie McIvor

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.

Author: Lucy Kirkham

Expertise: Head of STEM

Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.