A mutation that converts an amino acid codon to a stop codon is a:

Changes one codon for an amino acid into another codon for that same amino acid - Silent mutation Codon for one amino acid is changed into a codon of another amino acid - Missense mutation Codon for one amino acid is changed into a translation termination codon - Non-sense mutation Reading frame changes downstream to the mutant site - Frameshift mutation. A purine base replaced by another pyrimidine,  or  pyrimidine  replaced  by  another purine -Transversion. Key Concept Nonsense mutation A coding codon mutated to a nonsense codon result in premature termination of polypeptide chain.