Chain-termination codon: A set of three adjacent bases in the DNA or their complementary bases in messenger RNA that specifies the end of a polypeptide chain.
The three chain-termination codons (in messenger RNA) are UAA, UAG, and UGA. They are also called termination codons, stop codons, or nonsense codons.
U = uracil; A = adenine; G = guanine.
