Describe the role of messenger RNA (mRNA) and transfer RNA (tRNA) in the synthesis of a protein from a gene.

AQA A-Level Biology (7402) — 3.1.5 Nucleic Acids · Describe · 5 marks · View as Markdown

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

Model answer (5 marks)

mRNA is transcribed from the DNA gene and carries the genetic code from the nucleus to the ribosome.
The ribosome reads the mRNA in codons (triplets of bases).
tRNA brings specific amino acids to the ribosome.
The tRNA anticodon is complementary to the mRNA codon, ensuring amino acids are joined in the correct order to form the protein.

Examiner tips

Use the exact terms ‘transcribed’, ‘codon’, ‘anticodon’, ‘ribosome’ and ‘amino acid’
Show the flow: DNA → mRNA → ribosome → tRNA → protein
Keep the answer concise – 5 points, one sentence per point

Common mistakes

Confusing tRNA with rRNA or mRNA, or omitting the anticodon detail
Writing ‘mRNA is made from the gene’ instead of ‘transcribed from the DNA gene’
Failing to mention that the ribosome reads the mRNA in codons

Mark scheme (5 marks)

mRNA is made using the DNA gene as a template (in transcription)
mRNA carries the genetic code / sequence of bases from the nucleus to the ribosome
The ribosome reads the mRNA in codons / triplets of bases
tRNA carries / brings specific amino acids to the ribosome
The anticodon of tRNA is complementary to / matches the codon on mRNA, so amino acids are joined in the correct order to form the protein

Key terms in this question

messenger RNA (mRNA) · transfer RNA (tRNA)