Which mutation would you expect to disrupt translation termination by introducing a stop codon early?

Which mutation would you expect to disrupt translation termination by introducing a stop codon early?

• A. Missense
• B. Nonsense
• C. Silent
• D. Frameshift

Answer: (B)

A premature stop codon is the hallmark of a nonsense mutation. It changes a codon that would normally encode an amino acid into a stop signal, so translation terminates early and the resulting protein is truncated and typically nonfunctional. Missense mutations swap one amino acid for another and don’t create a stop signal. Silent mutations change a codon without altering the amino acid, so termination isn’t affected. Frameshift mutations alter the reading frame and can later generate a stop codon, but their main effect is shifting all downstream codons, not specifically introducing an early termination signal.

A premature stop codon is the hallmark of a nonsense mutation. It changes a codon that would normally encode an amino acid into a stop signal, so translation terminates early and the resulting protein is truncated and typically nonfunctional. Missense mutations swap one amino acid for another and don’t create a stop signal. Silent mutations change a codon without altering the amino acid, so termination isn’t affected. Frameshift mutations alter the reading frame and can later generate a stop codon, but their main effect is shifting all downstream codons, not specifically introducing an early termination signal.