Many, if not most, diseases have their roots in our genes. Genes - through the proteins they encode - determine how efficiently we process foods, how effectively we detoxify poisons, and how vigorously we respond to infections. More than 4,000 diseases are thought to stem from mutated genes inherited from one's mother and/or father. Common disorders such as heart disease and most cancers arise from a complex interplay among multiple genes and between genes and factors in the environment.

When a gene contains a mutation, the protein encoded by that gene will be abnormal. Some protein changes are insignificant, others are disabling.