What Is Missense Mutation?


Quick Answer

A missense mutation occurs when a gene is altered in a way that results in a different amino acid being substituted for the one originally coded. The change of a single nucleotide base can change the type of amino acid inserted into a protein.

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Full Answer

Amino acids bind together to make proteins. Each amino acid is made up of three nucleotide bases called codons. The nucleotide bases that make up amino acids are adenine, thymine, guanine and cytosine. Proteins have a precise lineup of many amino acids, and a change in just one amino acid can lead to a protein that functions abnormally or does not function at all.

A missense mutation in the gene coding for the protein hemoglobin substitutes the base thymine for adenine. This results in the insertion of the amino acid valine instead of glutamic acid. The resulting mutant hemoglobin clumps together. The red blood cells containing this mutant hemoglobin have a sickle shape instead of their normal disk shape.

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