454 Chapter 14 • Mutation, Repair, and Recombination Induced and spontaneous mutations arise by generally different mechanisms, and so they will be covered sepa-rately. After considering these mechanisms, we shall explore the subject of biological mutation repair. Without these repair mechanisms, the rate of mutation would be so high that cells would accumulate too many mutations to remain viable and capable of reproduction. Thus, the mutational events that do occur are those rare events that have some-how been overlooked or bypassed by the repair processes. Types of point mutations Point mutations are classiFed in molecular terms in Table 14-2, which shows the main types of DNA changes and their effects on protein function when they occur within the protein-coding region of a gene. The two main types of point mutation in DNA are base substitutions and base additions or deletions. Base sub-stitutions are mutations in which one base pair is replaced by another. Base substitutions also can be divided into two
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