A set of three nitrogen bases makes up a codon. The messenger RNA contains many such codons, with a series of three bases followed by three more bases, and then three more bases, and so on.
A codon represents either an amino acid or a stop codon. Some codons code for the same amino acid, like CUU and CUC both code for leucine (redundancy in sequences). All the codons together make up the genetic code that is read by the ribosome from the mRNA. Some examples of codons and their corresponding amino acids or a stop codon are:
- GCU – Alanine
- UAG – Stop
- GUG – Valine