Definition

A term that describes having two different versions of the same gene (one inherited from the mother and one inherited from the father). In a heterozygous genotype, each gene may have a different mutation (change) or one of the genes may be mutated and the other one is normal. For example, familial hypercholesterolemia (very high levels of cholesterol in the blood) can occur when a person is heterozygous for the LDLR gene, inheriting a mutated gene from one parent and a normal gene from the other parent.