Which type of mutation most directly causes translation of an mRNA to stop prematurely by creating a stop codon within the coding sequence?

• A. Silent (synonymous) mutation
• B. In-frame insertion (addition of 3 nucleotides)
• C. Missense mutation
• D. Nonsense mutation

Answer: (D)

Verified step by step guidance

1. Understand the types of mutations and their effects on the protein sequence: Silent mutations do not change the amino acid sequence; missense mutations change one amino acid; in-frame insertions add amino acids without disrupting the reading frame; nonsense mutations introduce a premature stop codon.
2. Recall that translation stops when a stop codon (UAA, UAG, or UGA) is encountered in the mRNA sequence during protein synthesis.
3. Identify that a nonsense mutation changes a codon that originally coded for an amino acid into a stop codon, causing translation to terminate prematurely.
4. Recognize that this premature stop codon results in a truncated protein, which can affect protein function significantly.
5. Conclude that among the given options, the mutation type that most directly causes early termination of translation by creating a stop codon is the nonsense mutation.