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Why can more than one codon specify the same amino acid?

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In biology, the genetic code is described as degenerate because most of the 20 amino acids are specified by more than one codon. While there are 64 possible triplet combinations of nucleotides, only 61 of these encode amino acids, while the remaining three serve as stop signals to terminate translation.12

This redundancy means that multiple codons can map to the same amino acid; for instance, leucine and serine can each be specified by six different codons. The structure of the genetic code, where many amino acids are uniquely determined by the first two bases of the codon, suggests that the code may have evolved from a more primitive system involving 16 dinucleotides.32

This degeneracy provides a biological buffer, as it allows for silent mutations—where a change in a DNA base pair results in a new codon that still codes for the same amino acid, thereby preserving the function of the resulting protein.4