A child is born with a condition that means some of the cells in their spinal cord are damaged and cannot carry out their normal function. Doctors discuss whether stem cell therapy could be used to replace the damaged cells. Explain how stem cells could be used to treat this condition, and outline ONE advantage and ONE disadvantage of using stem cells in this way.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Stem cells are undifferentiated cells found in embryos and in certain adult tissues. They can divide by mitosis and differentiate into specialised cell types. The spinal cord is part of the central nervous system (CNS).
Model answer (5 marks)
Stem cells are undifferentiated cells that can divide by mitosis to produce more cells.
They can differentiate into specialised cell types, for example nerve cells of the spinal cord.
The differentiated cells could replace the damaged spinal‑cord cells and restore normal CNS function.
Advantage: stem cells can generate large numbers of replacement cells, allowing treatment of conditions that were previously incurable.
Disadvantage: use of embryonic stem cells raises ethical issues because the embryo is destroyed, and there is a risk of immune rejection or uncontrolled cell growth.
They can differentiate into specialised cell types, for example nerve cells of the spinal cord.
The differentiated cells could replace the damaged spinal‑cord cells and restore normal CNS function.
Advantage: stem cells can generate large numbers of replacement cells, allowing treatment of conditions that were previously incurable.
Disadvantage: use of embryonic stem cells raises ethical issues because the embryo is destroyed, and there is a risk of immune rejection or uncontrolled cell growth.
Examiner tips
- Use the exact terms "undifferentiated", "mitosis", "differentiate", "spinal cord", "CNS"; mention replacement and restoration of function; give one clear advantage and one clear disadvantage.
- Structure answer with short bullet‑style points to match the 5 marks.
Common mistakes
- Confusing stem cells with mature cells; not mentioning mitosis or differentiation; giving an advantage that is not specific to stem cells; omitting the disadvantage or giving a generic disadvantage not linked to stem cell therapy.
Mark scheme (5 marks)
- Stem cells are undifferentiated / unspecialised cells that can divide (by mitosis) to produce more cells
- Stem cells can differentiate into specialised cell types / the specific type of cell needed (e.g. nerve / spinal cord cells)
- The differentiated cells could replace the damaged cells in the spinal cord / restore normal function to the CNS
- ONE valid advantage — e.g. could treat previously incurable conditions / could restore lost function / stem cells can produce large numbers of replacement cells / embryonic stem cells can differentiate into any cell type (totipotent/pluripotent)
- ONE valid disadvantage — e.g. ethical issues with using embryonic stem cells (embryo is destroyed) / risk of immune rejection / risk of uncontrolled cell division / stem cell therapy is not yet fully developed / reliable
Key terms in this question
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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