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Homozygous: GCSE Biology Definition

Emma Archbold

Written by: Emma Archbold

Reviewed by: Naomi Holyoak

Published

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1 minutes

Contents

  1. 1. What is a homozygous genotype?
  2. 2. Homozygous revision resources to ace your exams

What is a homozygous genotype?

In GCSE biology an organism is homozygous when the equivalent genes in a homologous pair of chromosomes have the same alleles as each other, e.g. when they are both recessive alleles or both dominant alleles.

Every person inherits two sets of chromosomes - one from the egg cell and one from the sperm cell. Chromosomes from each set that have the same genes are called homologous chromosomes. Someone with a homozygous genotype has the same alleles on the two homologous chromosomes. For genes with dominant/recessive alleles a genotype can be either homozygous recessive or homozygous dominant.

Different types of alleles in different genotypes
Alleles are different forms of the same gene. You can only inherit two alleles for each gene, and they can be the same (homozygous) or different (heterozygous).

Homozygous revision resources to ace your exams

You can explore homozygous genotypes further using our GCSE revision notes, topic questions and flashcards for your specific exam board:

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Reviewer
Emma Archbold

Author: Emma Archbold

Expertise: Biology

Prior to working at SME, Emma was a Biology teacher for 5 years. During those years she taught three different GCSE exam boards and two A-Level exam boards, gaining a wide range of teaching expertise in the subject. Emma particularly enjoys learning about ecology and conservation. Emma is passionate about making her students achieve the highest possible grades in their exams by creating amazing revision resources!

Naomi Holyoak

Author: Naomi Holyoak

Expertise: Biology

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.

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