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How does mutation provide the genetic variation needed for evolution?

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Four kittens with different fur patterns-three tabby and one black-and-white-lying together in a box, illustrating genetic variation among offspring. — heredity Each offspring is a combination of its two parents, receiving some dominant traits from its mother and others from its father.

Mutation is the fundamental source of genetic variation, providing the raw material necessary for evolution by natural selection.1

At its core, a mutation is a permanent alteration in the DNA sequence of an organism's genome. These changes can occur through accidents during DNA replication or exposure to environmental factors like radiation or reactive chemicals. By introducing new mutant alleles into a population—a process sometimes described as mutational pressure—mutation creates the genetic diversity upon which natural selection acts.123

While many mutations are deleterious or silent, some can be beneficial in specific environments. Once these variations exist, natural selection operates by favoring or discriminating against individuals based on their expressed phenotypes. Consequently, while mutation generates the initial variation, the frequency of these alleles within a population is ultimately shaped by the interaction between mutation, chance, and the selective pressures of the environment.143