Genetic code: Difference between revisions

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[[File:RNA-codon.svg|thumb|A series of codons in part of a [[messenger RNA]] (mRNA) molecule. Each codon consists of three [[nucleotide]]s, usually corresponding to a single [[amino acid]]. The nucleotides are abbreviated with the letters A, U, G and C. This is mRNA, which uses U ([[uracil]]). DNA uses T ([[thymine]]) instead. This mRNA molecule will instruct a [[ribosome]] to synthesize a protein according to this code.]]

The '''geneticGenetic code''' is thea set of rules used by living [[cell (biology)|cells]] to [[Translation (biology)|translate]] information encoded within genetic material ([[DNA]] or [[RNA]] sequences of nucleotide triplets or [[codon]]s) into [[protein]]s. Translation is accomplished by the [[ribosome]], which links [[proteinogenic amino acid]]s in an order specified by [[messenger RNA]] (mRNA), using [[transfer RNA]] (tRNA) molecules to carry amino acids and to read the mRNA three [[nucleotide]]s at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries.

The codons specify which amino acid will be added next during [[protein biosynthesis]]. With some exceptions,<ref name="pmid19131629">{{cite journal | vauthors = Turanov AA, Lobanov AV, Fomenko DE, Morrison HG, Sogin ML, Klobutcher LA, Hatfield DL, Gladyshev VN | title = Genetic code supports targeted insertion of two amino acids by one codon | journal = Science | volume = 323 | issue = 5911 | pages = 259–61 | date = Jan 2009 | pmid = 19131629 | pmc = 3088105 | doi = 10.1126/science.1164748 }}</ref> a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. The vast majority of [[gene]]s are encoded with a single scheme (see the [[Codon tables|RNA codon table]]). That scheme is often called the canonical or standard genetic code, or simply ''the'' genetic code, though [[#Variations|variant codes]] (such as in [[mitochondrion|mitochondria]]) exist.