What is a missense mutation?

What is a missense mutation?

• A. A base-pair substitution that results in a codon that codes for a different amino acid.
• B. A base-pair insertion causing a frameshift.
• C. A base-pair substitution that creates a stop codon.
• D. A base-pair substitution that does not change the amino acid.

Answer: (A)

A missense mutation is a nucleotide base change that alters a codon so it specifies a different amino acid in the protein. When a base-pair substitution occurs and the new codon codes for a different amino acid, the protein sequence changes at that position. This can affect the protein’s shape and function, depending on how different the new amino acid is and where the change occurs. In contrast, an insertion that shifts the reading frame causes a frameshift, not just a single amino acid change. A substitution that creates a stop codon is a nonsense mutation, which truncates the protein. A substitution that does not change the amino acid is a silent (synonymous) mutation.

A missense mutation is a nucleotide base change that alters a codon so it specifies a different amino acid in the protein. When a base-pair substitution occurs and the new codon codes for a different amino acid, the protein sequence changes at that position. This can affect the protein’s shape and function, depending on how different the new amino acid is and where the change occurs.

In contrast, an insertion that shifts the reading frame causes a frameshift, not just a single amino acid change. A substitution that creates a stop codon is a nonsense mutation, which truncates the protein. A substitution that does not change the amino acid is a silent (synonymous) mutation.