Genetics - alleles
Alleles may be either recessive or dominant.
- A recessive allele only shows if the individual has two copies of it. For example, the allele for blue eyes is recessive. You need two copies of this allele to have blue eyes.
- A dominant allele always shows, even if the individual only has one copy of it. For example, the allele for brown eyes is dominant. You only need one copy of it to have brown eyes. Two copies will still give you brown eyes.
Genotype describes the genetic make-up of an organism (the combination of alleles).
Phenotype describes the observable, physical characteristics that an organism has. This is often related to a particular gene.