A point mutation occurs in an mRNA sequence, changing a single nitrogenous base in a codon. However, the amino acid sequence of the synthesized polypeptide chain remains completely unchanged. Which salient feature of the genetic code is primarily responsible for this observation?

Step-by-step solution

When a point mutation changes a single base in an mRNA codon but the resulting amino acid sequence remains unchanged, it indicates that the new codon codes for the same amino acid as the original codon (a silent mutation). This observation is primarily due to the 'degenerate' nature of the genetic code, which means that some amino acids are coded by more than one codon. The code being unambiguous means one codon codes for only one amino acid, which does not explain why two different codons can code for the same ami