Genetic code: Difference between revisions

Revision as of 23:52, 31 March 2003

Revision as of 00:05, 7 July 2003

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[[de:Genetischer Code]][[eo:Genetika Kodo]][[es:Codón]][[pl:Kod genetyczny]]

The '''genetic code''' is a mapping that [[biological cell]]s use to [[translation (biology)|"translate"]] sequences of three [[nucleotide]] bases (called "triplets" or "[[codon]]s") into [[amino acid]]s. The mapping indicates, for example, that when the sequence "adenine, adenine, adenine" is encountered, the amino acid [[lysine]] should be produced. When the code is followed repeatedly, many amino acids are created, and are strung together to form [[protein]]s.

In the process of [[protein biosynthesis]], a sequence of DNA called a [[gene]] is first [[transcription|transcribed]] (copied) into RNA. The RNA is a sequence of repeating units (nucleotide bases). Each position in the RNA may have four possible "values", signified by the four types of bases: adenine, guanine, cytosine and uracil. This sequence of bases encodes a protein. A protein is a sequence of [[amino acid]]s. There are twenty possible amino acids. The RNA is broken up into units of three, called a '''codon'''. Each codon specifies one amino acid. For example, the RNA sequence UUUAAACCC specifies three codons (UUU-AAA-CCC), which each specify one amino acid. This RNA sequence, then, encodes a protein sequence three amino acids in length (as we will see, it encodes Phenylalanine-Lysine-Proline). There are sixty-four possible codons.