suppressor mutation (suppressor) In genetics, a second mutation that masks the phenotypic effects of an earlier mutation. This second mutation occurs at a different site in the genome (i.e. it is not a strict reversion). Intragenic suppression results from a second mutation that corrects the functioning of the mutant gene (e.g. a mutation of a different nucleotide in the same triplet, such that the codon then encodes the original amino acid). Intergenic suppression results from mutation of a different gene, the product of which compensates for the dysfunction in the first (e.g. a mutation that produces a mutant transfer-RNA molecule that inserts an amino acid in response to a nonsense codon, thus continuing a protein that would otherwise have been terminated). If a single suppressor mutation can suppress more than one existing mutation, it is said to be a supersuppressor. Compare REVERSE MUTATION.

suppressor mutation In genetics, a second mutation that masks the phenotypic effects of an earlier mutation. This second mutation occurs at a different site in the genome (i.e. it is not a strict reverse mutation); ‘intragenic suppression’ results from a second mutation that corrects the functioning of the mutant gene (e.g. a mutation of a different nucleotide in the same triplet, such that the codon then encodes the original amino acid); ‘intergenic suppression’ results from mutation of a different gene, the product of which compensates for the dysfunction in the first (e.g. a mutation that produces a mutant transfer-RNA molecule that inserts an amino acid in response to a nonsense codon, thus continuing a protein that would otherwise have been terminated). If a single suppressor mutation can suppress more than one existing mutation, it is said to be a supersuppressor.