Which statement best describes a mutation and its typical protein-level consequences?

• A. A mutation is a heritable change in DNA; consequences can include missense, nonsense, or silent changes in the resulting protein.
• B. A mutation is a temporary error that is always repaired immediately.
• C. A mutation always stops transcription.
• D. A mutation only affects RNA.

Answer: (A)

Mutations are heritable changes in DNA that can alter the information used to make a protein. Because the genetic code translates DNA codons into amino acids, a change in the DNA sequence can have several typical protein-level outcomes: a missense change where one amino acid is substituted for another, a nonsense change that introduces a premature stop codon truncating the protein, or a silent change where the amino acid remains the same due to codon redundancy. This is why the mutation option captures the common ways mutations influence protein structure and function. It’s also worth noting that not all mutations are repaired immediately, and some can affect RNA production or processing as well, but the core protein-level consequences described—missense, nonsense, or silent—are the key ideas.