Describe how a protein is made from the information stored in DNA. Include the role of messenger RNA (mRNA) in your answer.

AQA A-Level Biology (7402) — 3.4.2 DNA and Protein Synthesis · Describe · 5 marks · View as Markdown

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

Model answer (5 marks)

DNA is located in the nucleus and cannot leave it.
A section of DNA is transcribed into messenger RNA (mRNA).
The mRNA exits the nucleus and binds to a ribosome in the cytoplasm.
The ribosome reads the codon sequence on the mRNA.
Amino acids are joined in the order specified by the mRNA to form a protein.

Examiner tips

Use the exact sequence of steps: DNA → transcription → mRNA → ribosome → translation.
Mention that the ribosome reads codons and that amino acids are joined in that order.
Keep the answer concise and avoid unnecessary detail.

Common mistakes

Confusing DNA location (e.g., saying DNA is in the cytoplasm).
Omitting the role of transcription or the ribosome.
Using vague terms like "protein is made" without describing the steps.

Mark scheme (5 marks)

DNA is found in the nucleus (and cannot leave it)
A section of DNA is used as a template to make mRNA (transcription)
mRNA moves out of the nucleus to a ribosome (in the cytoplasm)
The ribosome reads the base sequence / code on the mRNA
Amino acids are joined together in a specific order / sequence to make a protein

Key terms in this question

DNA · messenger RNA (mRNA) · protein