In addition to random errors that occur when DNA is copied, damage can be caused by physical and chemical
agents known as mutagens. A mutagen is anything that can cause a mutation in DNA. Examples of mutagens include
high-energy radiation from X rays and ultraviolet radiation. Ultraviolet radiation from type of energy in sunlight that is
responsible for suntans and sunburns. Other mutagens include asbestos and the chemicals in cigarette smoke.