Here's why:

* Codon: A codon is a sequence of three nucleotides (A, U, G, or C) on mRNA that codes for a specific amino acid during protein synthesis. Each codon corresponds to a specific amino acid, or a "stop" signal.

* mRNA: Messenger RNA (mRNA) carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are made.

Let me know if you'd like to know more about codons and protein synthesis!