Here's why:
* Codons are triplets of nucleotides (three DNA or RNA bases) that code for a specific amino acid.
* Punctuation in the context of the genetic code refers to the signals that indicate the start and end of a gene.
* Start codon: AUG (methionine) signals the beginning of a gene.
* Stop codons: UAA, UAG, and UGA signal the end of a gene.
Therefore, punctuation is not encoded by specific codons, but rather by the presence of the start and stop codons within the genetic sequence.