What is a nonsense mutation?

What is a nonsense mutation?

• A. Inserts an amino acid
• B. Creates a stop codon
• C. Duplicates a gene
• D. Degrades mRNA

Answer: (B)

A nonsense mutation occurs when a single-nucleotide change converts a codon that normally codes for an amino acid into a stop codon (UAA, UAG, or UGA). This causes translation to terminate early, producing a shortened protein that is usually nonfunctional. The earlier the stop codon appears in the sequence, the more severe the impact on protein function. This concept is distinct from simply inserting an amino acid, duplicating a gene, or a process that degrades mRNA, which describe different genetic changes or cellular responses.

A nonsense mutation occurs when a single-nucleotide change converts a codon that normally codes for an amino acid into a stop codon (UAA, UAG, or UGA). This causes translation to terminate early, producing a shortened protein that is usually nonfunctional. The earlier the stop codon appears in the sequence, the more severe the impact on protein function. This concept is distinct from simply inserting an amino acid, duplicating a gene, or a process that degrades mRNA, which describe different genetic changes or cellular responses.