Which one of the following types of mutations can lead to a major change in the encoded protein? A. Insertion of a single nucleotide near the end of…
Which one of the following types of mutations can lead to a major change in the encoded protein?A. Insertion of a single nucleotide near the end of the coding sequence.B. Removal of a single nucleotide from the beginning of the coding sequence.C. Deletion of three consecutive nucleotides of a codon in the middle of the coding sequence.D. Deletion of four consecutive nucleotides in the middle of the coding sequence.
Select an option to attempt
Correct Answer: Option B
Explanation
Frameshift mutations — major vs. minor changes:Frameshift mutations caused by insertions or deletions NOT in multiples of 3 nucleotides alter the reading frame for all codons downstream of the mutation.• Option B: Removing 1 nucleotide from the beginning (position 1) → frameshift affects the ENTIRE protein — major change.• Option D: Deleting 4 nucleotides (not a multiple of 3) from within the sequence → frameshift from that point onwards — major change downstream.Minor changes would be:• Silent mutations (same amino acid)• Conservative substitutions• Deletion of exactly 3 bp (removes one amino acid, rest of protein unaffected)Answer: B and D cause major changes (both cause frameshifts).