A combination of three adjacent nucleotides, free or in a polynucleotide or nucleic acid molecule; often used with specific reference to the unit (codon or anticodon) specifying a particular amino acid in expression of the genetic code.
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tri·nu·cle·o·tide (')trī-'n(y)ü-klē-ə-.tīd n a nucleotide consisting of three mononucleotides in combination: CODON
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tri·nu·cleo·tide (tri-nooґkle-o-tīd) a polymer made up of three mononucleotides.Medical dictionary. 2011.