Translation (HL)

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•  Initiation of translation involves assembly of the components that carry out the process


The first stage of translation involves the assembly of the three components that carry out the process (mRNA, tRNA, ribosome)

  • The small ribosomal subunit binds to the 5’-end of the mRNA and moves along it until it reaches the start codon (AUG)
  • Next, the appropriate tRNA molecule bind to the codon via its anticodon (according to complementary base pairing)
  • Finally, the large ribosomal subunit aligns itself to the tRNA molecule at the P site and forms a complex with the small subunit

translation initiation

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•  Synthesis of the polypeptide involves a repeated cycle of events


  • A second tRNA molecule pairs with the next codon in the ribosomal A site
  • The amino acid in the P site is covalently attached via a peptide bond (condensation reaction) to the amino acid in the A site
  • The tRNA in the P site is now deacylated (no amino acid), while the tRNA in the A site carries the peptide chain


  • The ribosome moves along the mRNA strand by one codon position (in a 5’ → 3’ direction)
  • The deacylated tRNA moves into the E site and is released, while the tRNA carrying the peptide chain moves to the P site
  • Another tRNA molecules attaches to the next codon in the now unoccupied A site and the process is repeated

translation elongation

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•  Disassembly of the components follows termination of translation


The final stage of translation involves the disassembly of the components and the release of a polypeptide chain

  • Elongation and translocation continue in a repeating cycle until the ribosome reaches a stop codon 
  • These codons do not recruit a tRNA molecule, but instead recruit a release factor that signals for translation to stop
  • The polypeptide is released and the ribosome disassembles back into its two independent subunits

translation termination

Translation Summary Animation

Please Note:
In this animation the release factor is represented as being similar to a tRNA molecule
In reality, the release factor is a protein and would appear quite dissimilar to a tRNA molecule