Mutation

n. [ L. mutatio, fr. mutare to change: cf. F. mutation. See Mutable. ] Change; alteration, either in form or qualities. [ 1913 Webster ]

The vicissitude or mutations in the superior globe are no fit matter for this present argument. Bacon. [ 1913 Webster ]

2. (Biol.) Gradual definitely tending variation, such as may be observed in a group of organisms in the fossils of successive geological levels. [ Webster 1913 Suppl. ]

3. (Biol.) (a) As now employed (first by de Vries), a cellular process resulting in a sudden inheritable variation (the offspring differing from its parents in some well-marked character or characters) as distinguished from a gradual variation in which the new characters become fully developed only in the course of many generations. The occurrence of mutations, the selection of strains carrying mutations permitting enhanced survival under prevailing conditions, and the mechanism of hereditary of the characters so appearing, are well-established facts; whether and to what extent the mutation process has played the most important part in the evolution of the existing species and other groups of organisms is an unresolved question. (b) The result of the above process; a suddenly produced variation. Mutations can occur by a change in the fundamental coding sequence of the hereditary material, which in most organisms is DNA, but in some viruses is RNA. It can also occur by rearrangement of an organism's chromosomes. Specific mutations due to a change in DNA sequence have been recognized as causing certain specific hereditary diseases. Certain processes which produce variation in the genotype of an organism, such as sexual mixing of chromosomes in offspring, or artificially induced recombination or introduction of novel genetic material into an organism, are not referred to as mutation. [ Webster 1913 Suppl. +PJC ]

4. (Biol.) a variant strain of an organism in which the hereditary variant property is caused by a mutation{ 3 }. [ Webster 1913 Suppl. ]