Multiple Choice
Which type of mutation always produces a stop codon in the coding sequence (thereby prematurely terminating translation)?
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17. Mutation, Repair, and Recombination
Types of Mutations
Multiple Choice
Which of the following DNA mutations is a frameshift mutation?
A
Substitution that creates a stop codon (nonsense mutation)
B
Insertion of a single nucleotide into a coding sequence (not in a multiple of three)
C
Deletion of three nucleotides, removing one amino acid but preserving the reading frame (in-frame deletion)
D
Substitution of one nucleotide for another that changes one amino acid (missense mutation)
Verified step by step guidance1
Understand what a frameshift mutation is: it occurs when nucleotides are inserted or deleted from the DNA sequence in numbers not divisible by three, which shifts the reading frame of the codons during translation.
Review each mutation type given: a substitution creating a stop codon is a nonsense mutation, which changes a codon to a stop codon but does not shift the reading frame.
Consider the insertion of a single nucleotide: since it is not a multiple of three, this insertion shifts the reading frame, altering every downstream codon and potentially changing the entire amino acid sequence.
Look at the deletion of three nucleotides: because three nucleotides correspond to one codon, this deletion removes one amino acid but keeps the reading frame intact, so it is an in-frame deletion, not a frameshift.
Examine the substitution of one nucleotide for another that changes one amino acid: this is a missense mutation, which alters a single codon but does not affect the reading frame.
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