Nonsense vs. missense vs. silent mutations
A point mutation changes an mRNA codon from UAC (tyrosine) to UAA. This mutation is:
Answer A: explanation for every choice
A
Correct. UAA is a stop codon, so translation ends early and the protein is truncated.
B
A missense mutation changes one amino acid to a different amino acid.
C
A silent mutation creates a codon for the same amino acid.
D
A frameshift results from an insertion or deletion that is not a multiple of three. This is a substitution.
TakeawayStop codons: UAA, UAG, UGA.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb19.