Although all normal human insulin molecules contain a specific sequence of amino acids, the nucleotide sequence in the insulin gene may vary slightly from person to person. This variation can occur because:
A. A specific codon can be represented by more than one polypeptide
B. The type of amino acids in insulin does not affect its function
C. A specific amino acid can be represented by more than one codon
D. The sequence of amino acids in insulin does not affect its function