Genetic code

The instructions in a gene that tell the cell how to make a specific protein. A, T, G, and C are the "letters" of the DNA code. They stand for the chemicals adenine, thymine, guanine, and cytosine, respectively, that make up the nucleotide bases of DNA. Each gene's code combines the four chemicals in various ways to spell out 3-letter "words" that specify which amino acid is needed at every step in making a protein. The discovery of the genetic code clearly ranks as one of the premiere events in what has been called the Golden Age of Biology and Medicine.

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genetic code n the biochemical basis of heredity consisting of codons in DNA and RNA that determine the specific amino acid sequence in proteins and that appear to be uniform for all known forms of life

genetic coding n

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the code in which genetic information is carried by DNA and messenger RNA. This information determines the sequence of amino acids in every protein and thereby controls the nature of all proteins made by the cell. The genetic code is expressed by the sequence of nucleotide bases in the nucleic acid molecule, a unit of three consecutive bases (a codon) coding for each amino acid. The code is translated into protein at the ribosomes (see transcription, translation). Any changes in the genetic code result in the insertion of incorrect amino acids in a protein chain, giving a mutation.

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the arrangement of consecutive nucleotide triplets (codons) in a nucleic acid that specifies the sequence of amino acids for synthesis of a protein (see accompanying table). See also transcription and translation.