What is the difference between a missense and a nonsense mutation?

What is the difference between a missense and a nonsense mutation?

• A. Missense changes one amino acid; nonsense creates a premature stop codon.
• B. Missense creates a stop codon; nonsense changes one amino acid.
• C. Missense changes DNA sequence; nonsense changes RNA editing.
• D. Missense is silent; nonsense is frameshift.

Answer: (A)

Mutations in the protein-coding sequence can impact the protein in different ways. A missense mutation changes one codon so it specifies a different amino acid in the growing chain. A nonsense mutation changes a codon to a stop signal, causing translation to terminate early and producing a truncated protein. The effect of a missense depends on how different the new amino acid is and where it sits in the protein—some substitutions are tolerated, others disrupt function. Nonsense mutations usually have more drastic consequences because they shorten the protein, often leading to loss of function or rapid degradation of the mRNA. The other ideas don’t fit because they swap the outcomes (missense creating a stop) or mix up the level of the change (DNA vs RNA) or describe silent or frameshift effects that aren’t characteristic of these two mutation types.

Mutations in the protein-coding sequence can impact the protein in different ways. A missense mutation changes one codon so it specifies a different amino acid in the growing chain. A nonsense mutation changes a codon to a stop signal, causing translation to terminate early and producing a truncated protein. The effect of a missense depends on how different the new amino acid is and where it sits in the protein—some substitutions are tolerated, others disrupt function. Nonsense mutations usually have more drastic consequences because they shorten the protein, often leading to loss of function or rapid degradation of the mRNA. The other ideas don’t fit because they swap the outcomes (missense creating a stop) or mix up the level of the change (DNA vs RNA) or describe silent or frameshift effects that aren’t characteristic of these two mutation types.