Homozygote: A person who has two identical forms of a particular gene, one inherited from each parent.

For example, a girl who is a homozygote for cystic fibrosis (CF) received the CF gene from both of her parents and therefore has CF.

The opposite of a homozygote is a heterozygote, a person who has two different forms of a particular gene. For example, the father and mother of a CF child are heterozygotes for cystic fibrosis (CF). Each carries one normal gene and one CF gene but has no signs or symptoms of the disease.