Missense mutations change a codon to code for a different amino acid, whereas nonsense mutations create a premature stop codon.

Missense mutations change a codon to code for a different amino acid, whereas nonsense mutations create a premature stop codon.

• A. Missense changes a codon to a stop codon; Nonsense changes a codon to a different amino acid.
• B. Missense changes a codon to a different amino acid; Nonsense creates a premature stop codon.
• C. Missense deletes a nucleotide; Nonsense duplicates a codon.
• D. Missense alters introns; Nonsense alters exons.

Answer: (B)

Missense and nonsense mutations are two ways a single-nucleotide change can alter the protein sequence. A missense mutation changes the codon so that it now codes for a different amino acid, which can alter the protein’s properties without stopping translation. A nonsense mutation converts a codon into a stop signal, causing translation to terminate early and producing a truncated protein. This is why the correct description is that missense changes a codon to a different amino acid, while nonsense creates a premature stop codon. The other statements mix up the effects (for example, describing deletions or duplications, or altering noncoding regions) and don’t reflect how these two mutation types operate in coding sequences.

Missense and nonsense mutations are two ways a single-nucleotide change can alter the protein sequence. A missense mutation changes the codon so that it now codes for a different amino acid, which can alter the protein’s properties without stopping translation. A nonsense mutation converts a codon into a stop signal, causing translation to terminate early and producing a truncated protein. This is why the correct description is that missense changes a codon to a different amino acid, while nonsense creates a premature stop codon. The other statements mix up the effects (for example, describing deletions or duplications, or altering noncoding regions) and don’t reflect how these two mutation types operate in coding sequences.