Changes in the DNA sequence of single genes that can cause thousands of diseases. A gene can mutate in several ways which result in an altered protein that is unable to perform a normal function. The most common causes a “misspelling” in a single base in the DNA. Other include the loss (deletion) or gain (duplication or insertion) of single or multiple bases (s). The altered protein product may still retain some normal function but at a reduced capacity. In other cases, the protein may be totally disabled by the mutation or gain an entirely new, but damaging, function. The outcome depends on how it alters a protein’s function and how vital that protein is to survival.