Can an amino acid have multiple triplet codes?

• A. No
• B. Yes
• C. Sometimes
• D. Not specified

Answer: (B)

The genetic code is redundant: there are more codons (triplets) than there are amino acids. Because of this, a single amino acid can be specified by several different codons. During translation, mRNA codons pair with tRNA anticodons to bring in amino acids, and the same amino acid can be coded by multiple codons, giving the observed degeneracy.

For example, leucine can be encoded by six different codons (UUA, UUG, CUU, CUC, CUA, CUG), and serine by six as well (UCU, UCC, UCA, UCG, AGU, AGC). Isoleucine, on the other hand, has three codons (AUU, AUC, AUA). This redundancy means a change in the third base of a codon often does not alter the amino acid specified, which helps protect against some mutations. So an amino acid can indeed have multiple triplet codes.