Silent Mutation

Silent Mutation

Silent mutations are DNA mutations that do not result in a change to the amino acid sequence of a protein, or that do result in amino acid change but do not result in radically different properties of the changed amino acids. They may occur in a non-coding region (outside of a gene or within an intron), or they may occur within an exon in a manner that does not alter the final amino acids' behaviors. Mutations that cause the altered codon to produce an amino acid with similar functionality (i.e. a mutation producing leucine instead of isoleucine) are often also classified as silent; if the properties of the amino acid are conserved, this mutation does not usually significantly affect protein function. The phrase silent mutation is often used interchangeably with the phrase synonymous mutation; however, synonymous mutations are a subcategory of the former, occurring only within exons.

Because silent mutations do not alter protein function they are often treated as though they are evolutionarily neutral. However, many organisms are known to exhibit codon usage biases, suggesting that there is selection for the use of particular codons due to translational stability. Silent mutations may also affect splicing, or transcriptional control.

In molecular cloning experiments, it can be useful to introduce silent mutations into a gene of interest in order to create or remove recognition sites for restriction enzymes.

Recent results suggest that silent mutations can have an effect on subsequent protein structure and activity.