Explain how a molecule of transfer RNA (tRNA) contributes to the production of a protein during translation.

Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 1.4 DNA, RNA and protein synthesis · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Transfer RNA (tRNA) molecules are found in the cytoplasm and play an essential role during translation at the ribosome.

Model answer (5 marks)

tRNA carries a specific amino acid to the ribosome.
The tRNA has an anticodon that is complementary to a codon on the mRNA.
The anticodon sequence determines which amino acid the tRNA carries.
The amino acids are joined together in the order dictated by the mRNA codons, forming a polypeptide chain.
Thus the sequence of codons on the mRNA controls the sequence of amino acids in the protein.

Examiner tips

  • Use the word "anticodon" and "codon" explicitly. Show the link between anticodon, amino acid and protein sequence. Keep each point short and to the point to hit all five marks.

Common mistakes

  • Confusing tRNA with mRNA or rRNA. Forgetting to mention that the anticodon is complementary to the codon. Using vague terms like "helps" instead of "carries" or "determines".

Mark scheme (5 marks)

  1. tRNA carries/brings a specific amino acid to the ribosome
  2. tRNA has an anticodon that is complementary to / pairs with a codon on the mRNA
  3. each tRNA molecule carries a specific/particular amino acid determined by its anticodon sequence
  4. amino acids are joined together (in sequence) to form a polypeptide / protein chain
  5. the sequence of codons on mRNA determines the order in which tRNA molecules deliver amino acids, giving a specific sequence of amino acids in the protein

Key terms in this question

transfer RNA (tRNA) · translation

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