Genetic code: Difference between revisions

Revision as of 09:21, 30 January 2004

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[[de:Genetischer Code]] [[eo:Genetika Kodo]] [[es:Codón]] [[ja:遺伝暗号]] [[nl:Genetische code]] [[pl:Kod genetyczny]]

The '''genetic code''' is a [[mapping]] that [[biological cell]]s use to [[translation (biology)|translate]] sequences of three [[nucleotide]] bases, called '''codons''' or '''triplets''', into [[amino acid]]s. Nearly all living things use the same genetic code, called the '''standard genetic code''', and all use small variations of it. The code is followed repeatedly, creating many amino acids strung together into a [[protein]].

This process is called [[protein biosynthesis]]. First, a sub-sequence of [[DNA]] called a [[gene]] is [[transcription|transcribed]] (rewritten) into [[RNA]]. An RNA is a sequence of repeating nucleotide bases. ThereThe arebases fourin typesRNAs of base:are [[adenine]], [[guanine]], [[cytosine]] and [[uracil]]. The RNA is divided into groups of three bases, called codons. Each codon represents one amino acid. There are 64 possible codons. For example, the RNA sequence UUUAAACCC contains the codons UUU, AAA and CCC, each of which specifies one amino acid. So, this RNA sequence represents a protein sequence, three amino acids long. (In [[DNA]] is also sequence of nucleotide bases, thebut basethere [[thymine]] takes the place of uracil.)

The standard genetic code is shown in the following tables. [[#Table 1: Codon Table|Table 1]] shows what amino acid each of the 4³ = 64 codons specifies. [[#Table 2: Reverse Codon Table|Table 2]] shows what codons specify each of the 20 standard amino acids involved in translation. These are called forward and reverse codon tables, respectively. For example, the codon GAU represents the amino acid [[asparagine]] (Asp), and [[cysteine]] (Cys) is represented by UGU and by UGC.