452 Chapter 14 • Mutation, Repair, and Recombination CHAPTER OVERVIEW G enetic variation among individuals provides the raw material for evolution. Because genetics is the study of inherited differences, genetic analysis would not be possible without variants— individuals that show phe-notypic differences in one or more particular characters. In previous chapters we performed many analyses of the inheritance of such variants; now we consider their ori-gin. How do genetic variants arise? Two major processes are responsible for genetic vari-ation, mutation and recombination . We have seen that mutation is a change in the DNA sequence of a gene. Mutation is the ultimate source of evolutionary change; new alleles arise in all organisms, some spontaneously, others as a result of exposure to radiation and chemicals in the environment. The new alleles produced by muta-tion become the raw material for a second level of varia-tion, effected by recombination. As its name suggests, recombination is the outcome of cellular processes that
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