Recessive Allele

Key Stage 4

A Recessive allele is an allele which can only be expressed in the phenotype when there are two copies of that allele.

When a genotype includes one dominant allele and one recessive allele the physical appearance of the person will be based on the dominant allele.

When there are two copies of the recessive allele the physical appearance of the person will be based on the recessive allele.

In a Punnett Square or Genetic Cross Diagram dominant alleles are written with a capital letter while the recessive alleles are written with a lower case letter.