Some mutations may include the loss or gain of a base, or certain segments of DNA may either multiply or disappear. The cells create proteins by copying the information from a gene, base by base. An error in one of the bases can result in an altered protein. The altered protein may have no effect, or it's intended function may be totally disabled. There are many other factors that influence whether or not a mutation in a particular gene is expressed.
Cells are often able to recognize and repair certain mutations.
In many cases, a genetic mutation does not have complete penetrance . This means that even though a person may carry a dominant gene for a particular disorder, that disorder may not actually occur. Or in some cases, mutations in more than one gene are required to produce a particular trait. Some disorders may require a combination of both genetic mutation and environmental factors to appear. Autosomal dominant HSP usually exhibits complete penetrance.