Explain how monoclonal antibodies are produced and describe one way in which they can be used to treat cancer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
1. A specific antigen is selected and injected into a mouse to stimulate an immune response.
2. B‑lymphocytes that produce the desired antibody are collected from the mouse.
3. These lymphocytes are fused with tumour cells to form hybridoma cells.
4. The hybridoma cells are cloned and cultured to produce large quantities of identical (monoclonal) antibodies.
5. Monoclonal antibodies can be conjugated to a toxic drug or radioactive substance; they bind specifically to antigens on cancer cells, delivering the drug directly to the tumour and killing cancer cells without harming normal cells.
2. B‑lymphocytes that produce the desired antibody are collected from the mouse.
3. These lymphocytes are fused with tumour cells to form hybridoma cells.
4. The hybridoma cells are cloned and cultured to produce large quantities of identical (monoclonal) antibodies.
5. Monoclonal antibodies can be conjugated to a toxic drug or radioactive substance; they bind specifically to antigens on cancer cells, delivering the drug directly to the tumour and killing cancer cells without harming normal cells.
Examiner tips
- Use the exact sequence of steps; include ‘fused with tumour cells’ to show hybridoma formation.
- Mention ‘conjugated to a toxic drug or radioactive substance’ to show targeted therapy.
- Show that the antibodies are identical (monoclonal) and that they bind specifically to cancer antigens.
- Use UK spelling and correct terminology (B‑lymphocytes, hybridoma).
Common mistakes
- Confusing the mouse with a human donor; the mouse is the source of the antibody. Failing to mention the fusion with tumour cells to create hybridomas. Describing antibodies as ‘polyclonal’ instead of ‘monoclonal’.
Mark scheme (5 marks)
- A specific antigen is selected / an antigen is injected into a mouse to stimulate an immune response
- Lymphocytes (B-lymphocytes) that produce the desired antibody are collected from the mouse
- Lymphocytes are fused with tumour cells to form hybridoma cells
- Hybridoma cells are cloned / cultured to produce large quantities of identical (monoclonal) antibodies
- Monoclonal antibodies can be attached to a toxic drug / radioactive substance and bind specifically to antigens on cancer cells, delivering the drug directly to the tumour / killing cancer cells without harming normal cells
Key terms in this question
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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