Suppressor mutation

From EvoWiki

A suppressor mutation is a mutation that counters the phenotypic effect of a previous mutation.

For example, say a mutation causes the codon 'AGA' (which codes for the amino acid Arginine) to change to 'AGC' (which codes for the amino acid Serine, a very different amino acid to Arginine). A suppressor mutation may be one that changes the mutated codon to 'CGC' (which also codes for Arginine), or to 'AAG' (which codes for Lysine, a similar amino acid to Arginine), thereby reversing the effect the first mutation may have had on the function of the protein.

Suppressor mutations can occur in two forms - intragenic (within a gene) and intergenic (in another gene). The above example is the former type. An example of intergenic suppression may include a mutation, occurring after a mutation that negatively affects substrate binding to an enzyme, that changes the conformation of the substrate, causing it to reform the 'normal' enzyme-substrate complex.