Multiple Choice
Which best describes somatic mutations?
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17. Mutation, Repair, and Recombination
Types of Mutations
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Which of the following would result in a frameshift mutation?
A
Deletion of three consecutive nucleotides
B
Insertion of a single nucleotide into a coding sequence
C
Substitution of one nucleotide for another
D
Duplication of an entire gene
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.
Recall that codons are read in groups of three nucleotides, so any insertion or deletion of nucleotides in multiples of three will add or remove whole codons but will not shift the reading frame.
Analyze each option: deletion of three nucleotides removes one codon but does not shift the reading frame; substitution of one nucleotide changes a single base but does not affect the reading frame; duplication of an entire gene adds a large segment but does not cause a frameshift within the coding sequence.
Focus on the insertion of a single nucleotide: since one is not divisible by three, this insertion shifts the reading frame downstream of the mutation, altering every subsequent codon and potentially changing the entire amino acid sequence.
Conclude that only the insertion of a single nucleotide into a coding sequence results in a frameshift mutation because it disrupts the triplet reading frame of the genetic code.
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