Answer
d.
Work Step by Step
Option a. is incorrect. If a nucleotide were to be deleted, the reading frame would be shifted (called a frameshift mutation), and every amino acid after the deletion would be wrong.
Option b. is incorrect. If the start codon were to be changed, it may not be the start codon anymore, so the polypeptide would not be made.
Option c. is incorrect. The insertion of one nucleotide would also result in a frameshift mutation, and the polypeptide in question would not be made.
Option d. is correct. A substitution may not result in a different peptide being added because oftentimes, more than one codon codes for the same amino acid.
