Explain how the nuclear pore complex regulates the export of mature mRNA from the nucleus to the cytoplasm as part of the control of gene expression.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Mature mRNA must be bound by specific export proteins (e.g. NXF1) before it can pass through the nuclear pore complex. Only fully processed transcripts – with a 5′ cap, a poly‑A tail and all introns removed – are recognised and allowed to exit; incompletely processed RNAs are retained in the nucleus.
The nuclear pore complex functions as a selective channel; export of mRNA is an active, energy‑dependent process that requires GTP hydrolysis and the Ran‑GTP gradient.
By deciding which mRNA molecules are exported and when, the cell controls which proteins are ultimately translated, providing a post‑transcriptional level of gene‑expression regulation.
The nuclear pore complex functions as a selective channel; export of mRNA is an active, energy‑dependent process that requires GTP hydrolysis and the Ran‑GTP gradient.
By deciding which mRNA molecules are exported and when, the cell controls which proteins are ultimately translated, providing a post‑transcriptional level of gene‑expression regulation.
Examiner tips
- Mention the export receptor (NXF1) and the requirement for mature mRNA features; link the Ran‑GTP gradient to active transport; explain the regulatory outcome.
Common mistakes
- Confusing transcription with translation; forgetting the need for 5′ cap/poly‑A tail; claiming export is passive instead of active.
Mark scheme (4 marks)
- Mature mRNA must be associated with specific export proteins (mRNA-binding proteins / export receptors such as NXF1) to pass through the nuclear pore complex.
- Only fully processed (mature) mRNA — with 5′ cap, poly-A tail, and introns removed — is recognised and permitted to exit, so incompletely processed transcripts are retained in the nucleus.
- The nuclear pore complex acts as a selective channel; the export of mRNA is an active, energy-dependent process (requiring GTP hydrolysis / the Ran-GTP gradient).
- By controlling which mRNA molecules are exported and when, the cell can regulate which proteins are ultimately translated, providing a post-transcriptional level of gene expression control.
Key terms in this question
Related
- All IB DP Biology Higher Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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