Induced mutations

Induced mutations result from exposure to some outside agent such as chemicals
or radiation. It probably comes as no surprise to you to find out that
many chemicals can cause DNA to mutate. Carcinogens (chemicals that cause
cancers) aren’t uncommon; the chemicals in cigarette smoke are probably
the biggest offenders. In addition to chemicals that cause mutations, sources
of radiation, from X-rays to sunlight, are also mutagenic. A mutagen is any
factor that causes an increase in mutation rate. Mutagens may or may not
have phenotypic effects — it depends on what part of the DNA is affected.
The following sections cover two major categories of mutagens: chemicals
and radiation. Each causes different damage to DNA.