Genetic code: Difference between revisions

Revision as of 10:03, 30 January 2004

Revision as of 10:19, 30 January 2004

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It is notable that the standard genetic code contains features of basic [[error correction]]. Many codons which differ by only one base codes for the same amino acid, and most often the base that differs is the last base, which happens to be the base which is most often misread in the translation process. Furthermore, amino acids which tend to occur more frequently in proteins on average tend to have more codons which code for them.

Numerous variations of the standard genetic code are found in [[mitochondrion|mitochondria]], energy-burning [[organelles]] that probably evolved from [[symbiotic]] [[bacteria]]. [[Ciliate]] [[protozoa]] also showhave some variation in the genetic code: UAG and often UAA code for Glutamine (a variant also found in some [[green alga]]e), or UGA codes for Cysteine. Another variant is found in some species of the [[yeast]] [[Candidacandida]], where CUG codes for Serine. In some species of [[bacteria ]] and [[archaea]], a few non-standard amino acids are substituted for standard stop codons; UGA can code for [[selenocysteine]] and UAG can code for [[pyrrolysine]]. There may be other non-standard amino acids and codon interpretations thatbut are not known.

Despite these variations, the genetic codes used by all known forms of life on Earth are very similar. Since there are many possible genetic codes that are thought to have similar utility to the one used by Earth life, the theory of [[evolution]] suggests that the genetic code was established very early in the history of life.