Question

Frameshift mutations are those in which

• A. groups of three nucleotides get inserted or deleted
• B. a few nucleotides (not in multiples of three) get inserted or deleted
• C. a single nucleotide gets replaced by another
• D. the reading frame of the nucleotide sequence does not get shifted

Answer 1

The correct option is B a few nucleotides (not in multiples of three) get inserted or deleted

As the name indicates, frameshift mutations are those that result in a shift in the reading frame of the nucleotide sequence. Since a codon is made of three nucleotide bases, an insertion or deletion of three (or multiples of three) nucleotide bases would not result in a shift in the reading frame; it would rather result in extra codon(s) or missing codon(s) respectively. This eventually leads to a modified protein (due to missing or additional codons). Thus, they may be called non-frameshift mutations. However, if the number of nucleotide bases inserted or deleted is not a multiple of three, it would alter the reading frame and hence, can be called frameshift mutations.