Mutations and DNA Repair

Genomes are dynamic entities that change over time as a result of the cumulative effects of small-scale sequence alterations caused by mutation. A mutation is a change in the nucleotide sequence of a short region of a genome (Figure 16.1A). Many mutations are point mutations (also called simple mutations or single-site mutations) that replace one nucleotide with another. Point mutations are divided into two categories: transitions, which are purine-to-purine or pyrimidine-to-pyrimidine changes (A → G, G → A, C → T, or T → C), and transversions, which are purine-to-pyrimidine or pyrimidine-to-purine changes (A → C, A → T, G → C, G → T, C → A, C → G, T → A, or T → G). Other mutations arise from insertion or deletion of one or a few nucleotides. Figure 16.1 <bold>Mutation and DNA repair</bold>. (A) A mutation is a small-scale change in the nucleotide sequence of a DNA molecule. A point mutation is shown but there are several other types of mutation, as described in the text. (B) DNA repair corrects mutations that arise as errors in replication and as a result of mutagenic activity. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315226828/f9ea4da9-cd6e-4b1e-8944-b57304f0c315/content/fig16_1.tif"/>