translation (genetic)

Last reviewed 01/2018

Translation is the synthesis of a protein by ribosomes, using messenger RNA as a template.

• mRNA is 'read' by organelles called ribosomes in order to sythesis a particular polypeptide. Transfer (t) RNA is also required for this process. tRNA are specific for one particular amino acid and carries required amino acids to the ribosome in order to synthesise the polypeptide chain.

• the ribosome 'reads' the mRNA in the 5' to 3' direction. The coding part of the mRNA is made up of sets of three nucleotides (codon) which code for a specific amino acid or for the chain to stop. The total number of different codes possible is 64 (4x4x4); however there are only 20 different amino acids and so some amino acids are coded for by more than one codon.

• as each codon is 'read' the amino acids are carried to the site of formation of the polypeptide chain by the particular tRNA. Each tRNA has an anticodon (3 unpaired bases) that are opposite to the particular codon on the mRNA e.g. if the mRNA codon is AGG then the matching tRNA anticodon is UCC. Once a amino acid is bound to the forming polypeptide chain the next codon is read by the ribosome. The sequence of reading the mRNA and adding an amino acid continues until the 'stop' sequence is recognised.