Mutagenesis is the induction of genetic change in a cell by the alteration of DNA. The change or alteration is heritable in cell progeny and is almost always detrimental. While most mutations are indeed detrimental, it is well to remember that mutations provide the fabric of evolution. Further, many mutations have been economically valuable to humans. The Delicious apple is such a mutation.

Mutagenesis can result in alteration of an individual gene, a point mutation, or can result in aberrations in chromosome number and structure. If a mutagenic event occurs to a body cell, the cell may survive but it may show no observable effect, it may be lethal to the cell (which for the most part would also have no observable effect), it might be propagated as a useful variant (the example of the Delicious apple), or it may give rise to variant cells that produce either...