13.9 An intergenic suppressor mutation occurs in a gene other than the one bearing the original mutation. (a) The wild-type sequence produces a full-length, functional protein. (b) A base substitution at a site in the same gene produces a premature stop codon, resulting in a truncated, nonfunctional protein. (c) A base substitution at a site in another gene, which in this case encodes tRNA, alters the anticodon of tRNA^Tyr so that tRNA^Tyr can pair with the stop codon produced by the original mutation, allowing tyrosine to be incorporated into the protein and translation to continue.