Describe how non-coding DNA controls which proteins are produced in a cell.

Eduqas GCSE Biology — 2.4.1 Variation · Describe · 4 marks · View as Markdown

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

Human cells all contain the same genome, yet liver cells and muscle cells produce different proteins and carry out different functions.

Model answer (4 marks)

Non‑coding DNA does not code for a protein itself.
It regulates gene expression by switching genes on or off.
When a gene is switched on it is transcribed into mRNA.
Thus different cells produce different proteins, so not every protein is needed by every cell at all times.

Examiner tips

Use the phrase ‘switch genes on or off’ to show regulation. Show that transcription is the first step when a gene is active. Mention that different cells express different sets of genes.

Common mistakes

Confusing non‑coding DNA with coding DNA. Saying that non‑coding DNA *makes* proteins. Failing to explain that switching on leads to transcription.

Mark scheme (4 marks)

Non-coding DNA does not code for / is not used to make a protein (itself)
Non-coding DNA controls / regulates gene expression by switching genes on or off
When a gene is switched on it is active and can be used in protein synthesis / transcribed
This means different cells can produce different proteins / not every protein is needed by every cell at all times

Key terms in this question

non-coding DNA