Substitution mutations

A type of point mutation where one amino acid is substituted for another. This can have three possible effects on the overall protein.

Silent mutation: Change to the base sequence codes for the same amino acid as DNA code is degenerate. This means that the overall protein has the same structure, so there is no effect on its function.

Nonsense mutation: Change to a base sequence that changes the codon to a stop codon. This results in the formation of a truncated protein. Highly unlikely that the protein will have normal function in the body, so normally a negative effect on the organism.

Missense mutation: Change to a base sequence that means that the incorrect amino acid is incorporated into the polypeptide chain. This could either have no/very little effect if the amino acid is similar (conservative mutation), or it could have a large effect, for example if the mutation is in the active site region of an enzyme (non-conservative mutation).