You would find the codon on a messenger RNA (mRNA) molecule.

Here's why:

* Codons are three-nucleotide sequences within mRNA. They act as the "code" for specific amino acids during protein synthesis.

* During translation, ribosomes read these codons in the mRNA and bring in the corresponding amino acids to build a polypeptide chain.

Let me know if you'd like more information about codons or translation!