Any alteration in a gene from its natural state; may
be disease causing or a benign, normal variant
Definition from: GeneReviews
from the University of Washington and the National Center for Biotechnology Information
A mutation is a change in a DNA sequence. Mutations can result from DNA copying mistakes made during cell division, exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses. Germ line mutations occur in the eggs and sperm and can be passed on to offspring, while somatic mutations occur in body cells and are not passed on.