Allele - GCSE Biology Definition

What is an allele?

In GCSE biology, an allele is a version of a gene. Each individual has two alleles of each gene, one on each member of a homologous pair of chromosomes. The genotype of an individual is determined by the alleles present for each gene.

An individual with two identical alleles of a gene is said to be homozygous and an individual with two different alleles of a gene is referred to as heterozygous. Alleles that are dominant will always be expressed in the phenotype of an organism, while recessive alleles are only expressed in the phenotype if the dominant allele is absent.

Allele revision resources to ace your exams

You can explore the concept of alleles and inheritance further using our GCSE revision notes, topic questions and flashcards for your specific exam board:

• Genetic Inheritance (AQA GCSE Biology)

• Inheritance Key Definitions (Edexcel GCSE Biology)

• The Genome & Genetics (OCR GCSE Biology)

• Genes, Alleles and Other Key Terms in Genetics (WJEC GCSE Biology)
  

Meet all your GCSE biology revision needs using our revision resources linked below. This includes revision notes, videos, flashcards and exam questions with student-friendly mark schemes.

Explore GCSE Biology Revision Resources