Missense mutation
A missense mutation is a DNA sequence change that alters a codon so a different amino acid is placed in a protein.
What a missense mutation is
A missense mutation is a coding DNA change that causes one amino acid to be substituted for another in a protein. The word missense reflects that the codon still makes sense as an amino-acid instruction, but it now points to a different amino acid than before.
How codons change
Missense mutations often come from a single base substitution in a codon. For example, changing one nucleotide may turn a codon for one amino acid into a codon for another. Because the genetic code is redundant, not every base substitution is missense; some are silent, and some create stop codons.
Conservative and nonconservative changes
Some amino acid substitutions are conservative, meaning the new amino acid has similar size, charge, or chemistry to the original. Others are nonconservative and may disrupt folding, binding, stability, or activity. This chemistry is one reason different missense mutations can have very different outcomes.
Protein context matters
A missense mutation in an active site, binding surface, membrane-spanning region, or tightly packed structural core can be more consequential than a change in a flexible or less constrained region. The same amino acid change can also matter differently in different proteins.
Possible biological outcomes
A missense mutation may reduce protein function, create a new activity, alter regulation, affect localization, or have little measurable effect. In inherited disease and cancer, some missense variants are important drivers, while many others are benign or remain variants of uncertain significance.
How scientists interpret them
Interpreting a missense variant can involve population frequency, evolutionary conservation, protein structure, functional assays, family data, computational predictions, and clinical evidence. No single clue is perfect, so confident interpretation usually depends on multiple lines of evidence.
Comparison with other mutations
Missense mutations differ from nonsense mutations, which create a stop codon, and frameshift mutations, which change the downstream reading frame. They also differ from silent mutations, which change a codon without changing the encoded amino acid.
Why it matters
Missense mutations are a major bridge between DNA variation and protein behavior. They help explain how tiny sequence changes can alter enzymes, receptors, structural proteins, and disease risk. They are also central to variant classification, precision medicine, and protein engineering.