A mutation is an abrupt change in genes or chromosomes that affects an organism morphologically. Mutations can occur spontaneously or be induced by environmental factors, and, on occasion, they can even occur as the result of a change in chemistry within a cell. The process of creating a mutation is called mutagenesis. An organism that has a mutation is called a mutant, and something that creates a mutation is called a mutagen.

Mutations are the major cause of variability, which allows evolution to take place, although these random changes are far more likely to harm than to improve a complex organism. However, we can now deliberately select certain mutations (the favorable ones) to improve plants and animals. It is possible to create a specific mutation at will, rather than select among the array of random mutations for the infrequent useful ones. Mutation has been the most consistent way...