A mutation causing a stop codon is called

A mutation causing a stop codon is called

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

Answer: (A)

A stop codon mutation is called a nonsense mutation. It changes a codon that normally encodes an amino acid into a stop codon (UAA, UAG, or UGA in mRNA; DNA equivalents TAA, TAG, TGA), causing translation to terminate prematurely. The resulting protein is usually truncated and often nonfunctional. The effect depends on where the stop occurs: early stops produce shorter, more deleterious proteins, while later stops may have milder consequences or trigger decay of the mRNA. This differs from missense mutations, which swap one amino acid for another; silent mutations, which do not alter the amino acid sequence due to codon redundancy; and frameshift mutations, which shift the reading frame and alter many downstream residues.

A stop codon mutation is called a nonsense mutation. It changes a codon that normally encodes an amino acid into a stop codon (UAA, UAG, or UGA in mRNA; DNA equivalents TAA, TAG, TGA), causing translation to terminate prematurely. The resulting protein is usually truncated and often nonfunctional. The effect depends on where the stop occurs: early stops produce shorter, more deleterious proteins, while later stops may have milder consequences or trigger decay of the mRNA. This differs from missense mutations, which swap one amino acid for another; silent mutations, which do not alter the amino acid sequence due to codon redundancy; and frameshift mutations, which shift the reading frame and alter many downstream residues.