Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 27.07.2021

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Conversion of the information of the mRNA (the base sequence) into a protein (an amino acid sequence). Three nucleotides of the mRNA each encode an amino acid. This is bound to a specific transfer RNA (= tRNA) and is transported to the ribosome.

General information
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A distinction is made between:

  • the start codon
  • normal codons and
  • the stop codons.

Translation will always start at the start codon AUG (base triplet consisting of adenine, uracil and guanine) and end at one of the three stop codons (UGA, UAA or UAG).

"Normal" codons are all other base triplets that are neither start nor stop codons and each encode a specific amino acid. The start codon AUG additionally encodes an amino acid (methionine). The three stop codons are only responsible for terminating translation. They do not encode an amino acid.

At the start codon, the first tRNA (transfer RNA) now anneals to the mRNA (the start codon is AUG and the first annealing tRNA accordingly takes up the amino acid methionine). The tRNA has the task of transporting the individual amino acids to the ribosome and then linking them with another amino acid. This sequence gives rise to the peptide chains.

The tRNA consists of several arms. One arm binds an amino acid. On the opposite arm is the anticodon that matches the corresponding base codon of the mRNA. Example: The tRNA for methionine has the anticodon UAC; this only matches the base triplet AUG in the mRNA. Thus, the base sequence AUG in the mRNA encodes the amino acid methionine. Each tRNA is only responsible for one amino acid at a time, analogous to its anticodon. Thus, each amino acid requires a specific tRNA to be mediated to the corresponding codon on the mRNA. This is followed by a second tRNA with a corresponding amino acid, which is added next to the first tRNA. A peptide bond is formed between the two amino acids. After the attachment of the amino acid, the first tRNA leaves the ribosome. The attached amino acid is now located at the end of the arm of the second tRNA together with its amino acid. Furthermore, a third tRNA and its specific amino acid attach to the mRNA. The process is repeated until a base triplet appears in the mRNA that codes for a stop codon. There is no suitable tRNA for stop codons, so that the resulting peptide chain is now detached. The polypeptide strand is finalized.


Last updated on: 27.07.2021