Describe how genotype and phenotype are related and give an example.

Genotype relates to the alleles an organism has in their genes. Phenotype is a term relating to the expression of the gene itself.

An organism with a homozygous dominant gene may only show the dominant trait, and it may only pass on the dominant trait. The same may be said for an organism with a homozygous recessive gene.

Example:

Two parents are homozygous dominant for brown eyes. They will never have a blue eyed child. Two parents are homozygous recessive for blue eyes, so they will only ever have blue-eyed children.

However, an organism with heterozygous alleles will have the ability to pass on an allele for either the dominant or the recessive traits. Heterozygous genes will always express the dominant trait.

Example:

A brown eyed woman, and a blue eyed man have a child. The child is born with brown eyes, but that child reproduces with someone many years later and that new child does have blue eyes.