In the
genetic code, a
stop codon (or
termination codon) is a
nucleotide triplet within
messenger RNA that signals a termination of
translation.
Proteins are based on polypeptides, which are unique sequences of
amino acids. Most
codons in messenger RNA (from DNA) correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein. Stop codons signal the termination of this process by binding
release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain. While start codons need nearby sequences or initiation factors to start translation, a stop codon alone is sufficient to initiate termination.