Recessive alleles are only expressed in the phenotype if there are two copies of the allele. Let's go back to our example with the eyes!
Do you remember how dominant genes work?
- They show their effect even if the individual only has one copy of the allele.
- This is known as being heterozygous.
- If you have the allele for brown eyes, you'll have brown eyes.
- If you have one copy of the brown eyes, you still will have brown eyes.
- However, this is where recessive alleles are different - they're the opposite really.
Let's go back to the chart by our friends at Genome Research Limited.
Recessive Alleles
- Recessive allele only show their effect if the individual has two copies of the allele.
- This is called being homozygous.
- For example, the blue eyes are recessive, so to have blue eyes, you need to have two copies of the 'blue eye' allele.
- Even if you have one copy of the blue-eye allele, if you have another allele, it won't be expressed.