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Mutation Rate During Cell Division

Every time a cell divides, the entire DNA sequence must be copied. In humans, this means copying about 12 billion nucleotides (both DNA strands of a diploid cell). The enzyme responsible for this process, DNA polymerase, is extremely accurate and makes only about one mistake per 100 million nucleotides (Griffiths et al., 2019).

Even with this high accuracy, the large size of the human genome means that hundreds of new mutations can appear during each cell division. Most of these errors are corrected by DNA repair systems or by the proofreading function of DNA polymerase, which fixes about 99% of mistakes.