- This article concerns biological mutants; for fictional aspects see Mutant (fictional)
A mutant (also known to early geneticists a "monster") is an individual, organism, or new genetic character arising or resulting from an instance of mutation, which is a sudden structural change within the DNA of a gene or chromosome of an organism resulting in the creation of a new character or trait not found in the parental type. In an organism or individual, the new character or trait may or may not be trivial, but it is rarely beneficial and will usually result in either a genetic disorder or have no observable effect whatsoever.
Occasionally, a body cell in a healthy organism may acquire a mutation caused by a genetic error occurring during routine cell division. Such an error may result in cancer.