stop codon

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stop codon (termination codon) The triplet of nucleotides on a messenger RNA molecule (see codon) at which the process of translation ends. It is recognized by proteins called release factors, which bind to the A site of the ribosome. This effectively stops the formation of a polypeptide chain at that point. The three stop codons are UGA, UAA, and UAG (see genetic code). Compare start codon.