A nonsense mutation introduces what?

A nonsense mutation introduces what?

• A. A stop codon is added.
• B. The amino acid is changed to another.
• C. No change to the amino acid.
• D. The reading frame shifts.

Answer: (A)

A nonsense mutation converts a codon that normally codes for an amino acid into a stop codon, so translation terminates sooner than usual. This creates a truncated protein, often losing function because important regions are missing. That makes “a stop codon is added” the best description of the effect. If the mutation merely changes one amino acid to another, that’s a missense mutation, not nonsense. If the codon still codes for the same amino acid, that’s a silent mutation. If nucleotides are inserted or deleted and the reading frame shifts, that’s a frameshift mutation, which is a different type of change.

A nonsense mutation converts a codon that normally codes for an amino acid into a stop codon, so translation terminates sooner than usual. This creates a truncated protein, often losing function because important regions are missing. That makes “a stop codon is added” the best description of the effect. If the mutation merely changes one amino acid to another, that’s a missense mutation, not nonsense. If the codon still codes for the same amino acid, that’s a silent mutation. If nucleotides are inserted or deleted and the reading frame shifts, that’s a frameshift mutation, which is a different type of change.