A word familiar to all fans of science fiction, mutation refers to any sudden change in DNA—deoxyribonucleic acid, the genetic blueprint for an organism—that creates a change in an organism's appearance, behavior, or health. Unlike in the sci-fi movies, however, scientists typically use the word mutant as an adjective rather than as a noun, as, for example, in the phrase "a mutant strain." Mutation is a phenomenon significant to many aspects of life on Earth and is one of the principal means by which evolutionary change takes place. It is also the cause of numerous conditions, ranging from albinism to cystic fibrosis to dwarfism. Mutation indicates a response to an outside factor, and the nature of that factor can vary greatly, from environmental influences to drugsto high-energy radiation.