Mutation

Abstract

A mutation is a DNA change that is recorded durably and passed on to the offspring. A number of mutations in germ cells have detrimental effects for they often cause hereditary diseases. Likewise, mutations that accumulate in body cells can generate cancers. Nevertheless, a large number of mutations are neutral in their normal environment. The few advantageous mutations that occur are generally maintained. Mutations that arise at random are constantly sifted through by a selective environment. This dual process works as the driving force of evolution.

Keywords: mutation; carcinogen; ames test; DNA damage; DNA replication error

Figure 1.

Types of mutation. (a) Wild‐type original sequence; (b) transition from C to T; (c) transversion from G to C; (d) deletion (Del) of the sequence ACCTA, the sign indicates from where it has been removed; (e) insertion (Ins) of the sequence AAAGC, the two signs indicate where the sequence has been inserted.

Figure 2.

Types of substitutions in a protein‐coding region: (a) synonymous, (b) missense, and (c) nonsense. In each case, the top sequence is wild type and the bottom sequence is mutated.

Figure 3.

Examples of frameshifts caused by deletion or insertion. (a) A deletion of a G causes premature termination. (b) An insertion of a G obliterates a stop codon. Termination codons are underlined. In each case, the top sequence is wild type and the bottom sequence is mutated.

Figure 4.

Generation of duplications or deletions by slipped‐strand mispairing between contiguous repeats (bold red). Small arrows indicate the direction of DNA synthesis. Dots indicate base pairing. (a) A two‐base slippage in a TA repeat during DNA replication. Slippage in the 3′ → 5′ direction results in the insertion of one TA unit (left panel). Slippage in the other direction results in the deletion of one repeat unit (right panel). The deletion shown in the right panel results from excision of the unpaired repeat unit (asterisks) at the 3′ end of the growing strands, presumably by the 3′ → 5′ exonuclease activity of DNA polymerase. (b) A two‐base slippage in a TA repeat in nonreplicating DNA. Mismatched regions form single‐stranded loops, which may be targets of excision or mismatch repair. The outcome (a deletion or an insertion) will depend on which strand is excised or repaired and which strand is used as template in the DNA repair process.

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Further Reading

Ames BN (1979) Identifying environmental chemicals causing mutations and cancer. Science 204: 587–593.

Ames BN, Shigenaga MK and Hagen TM (1993) Oxidants, antioxidants, and the degenerative diseases of aging. Proceedings of the National Academy of Sciences of the USA 90: 7915–7922.

Devoret R (1979) Bacterial tests for potential carcinogens. Scientific American 241: 40–50.

Echols H and Goodman MF (1991) Fidelity mechanisms in replication. Annual Review of Biochemisty 60: 477–511.

Friedberg EC, Walker GC and Siede W (1995) DNA Repair and Mutagenesis. New York: AMSPress.

Griffiths JF, Gelbart WM, Lewontin RC and Miller JH (2002) Modern Genetic Analysis (Integrating Genes and Genomes). New York: Freeman.

Klein J and Takahata N (2002) Where Do We Come From? The Molecular Evidence for Human Descent. Berlin: Springer.

Li WH and Graur D (1991) Fundamentals of Molecular Evolution. Sunderland, MA: Sinauer.

Radman M and Wagner R (1988) The high fidelity of DNA duplication. Scientific American 259: 40–46.

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How to Cite close
Devoret, Raymond(Mar 2004) Mutation. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001882]