Stop codon facts for kids

A stop codon is special sequence in the genetic code. It is a nucleotide triplet in messenger RNA that signals the end of translation.

It is a codon (that is, a sequence of three nucleotides in messenger RNA). It indicates the end of a gene. Similar to how a full stop indicates the end of a sentence, a stop codon signals the end of genetic translation.

They are also called termination codons or chain termination codons. There are three such codons: UAA, UAG and UGA.

Proteins are based on polypeptides, which are unique sequences of amino acids. Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein. Stop codons indicate the end of this process, and therefore, the end of polypeptide synthesis.