codon

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A codon is the three-unit sequence (AUG, AGC, etc.) of mRNA nucleotides that codes for a specific amino acid. Since there are only twenty commonly used amino acids and sixty-four (4x4x4) possible codon sequences, the genetic code is described as both degenerate and unambiguous. Each codon codes for only one amino acid, but each amino acid may have more than one matching codon.

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(koh-don)

A group of three bases on the DNA molecule. Each codon determines the identity of one amino acid in proteins made by the cell.

any group of three consecutive nucleotide bases (base triplet) in a given messenger RNA molecule that, by its composition and sequence, specifies either a particular amino-acid residue in the polypeptide chain synthesized by translation of that messenger RNA, or signals the beginning or the end of the message (i.e. start codon, stop codon). The term is also used loosely for base triplets in the genomic nucleic acid — in the case of duplex DNA, either on the coding strand or noncoding strand. For the full set of codons see genetic code.

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A triplet in a chain of nucleic acids in mRNA that specifies the order in which amino acids are added. The codon triplet pairs with a sequence of three complementary nucleotides, called the anticodon, present in the anticodon arm of tRNA. Called also triplet. See also deoxyribonucleic acid.

• start c. — see initiation codon.
• stop c's — three codons, UAG, UAA and UGA, also referred to as amber, ochre and opal codons, in mRNA which terminate translation.
• termination c. — see stop codons (above).

For a list of words related to codon, see:

• Genetics, Heredity, and Evolution - codon: sequence of three nitrogenous bases representing specific amino acid

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