This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
A mutation that converts an amino acid codon to a stop codon is a: 
Select and explain. 
A. Nonsense mutation, B. Transversion, C. Silent mutation, D. Frame shift mutation
A: Nonsense mutation
Answer: A: Nonsense mutation 
Explanation: 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.