A doctor is considering two types of stem cell therapy to treat a patient who has developed a degenerative nerve disease. The doctor is deciding between using adult stem cells taken from the patient's own bone marrow and using embryonic stem cells. Explain why embryonic stem cells and adult stem cells differ in their potential to treat this disease, and suggest one ethical issue associated with using embryonic stem cells.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Degenerative nerve diseases destroy specialised neurones in the central nervous system over time. Scientists are investigating stem cell therapies that could replace the lost neurones.
Model answer (5 marks)
Embryonic stem cells are pluripotent and can differentiate into any cell type, including neurones, so they can be directed to replace lost nerve cells in the CNS.
Adult stem cells from bone marrow are multipotent and can only become a limited range of cell types, usually blood and bone cells, so they are unlikely to generate the required neurones.
Thus embryonic stem cells have a greater therapeutic potential for degenerative nerve disease.
An ethical issue with embryonic stem cells is that obtaining them requires destroying the embryo, which many people consider to be the loss of a potential human life.
Adult stem cells from bone marrow are multipotent and can only become a limited range of cell types, usually blood and bone cells, so they are unlikely to generate the required neurones.
Thus embryonic stem cells have a greater therapeutic potential for degenerative nerve disease.
An ethical issue with embryonic stem cells is that obtaining them requires destroying the embryo, which many people consider to be the loss of a potential human life.
Examiner tips
- Use the terms pluripotent and multipotent; link totipotency to the ability to form any cell type. Show the logical chain: pluripotent → can become neurones → better for disease. Mention the specific limitation of adult stem cells. State a clear ethical concern about embryo destruction.
Common mistakes
- Confusing pluripotent with totipotent; both are correct but pluripotent is the key term. Failing to explain the link between cell potency and therapeutic ability. Giving an irrelevant ethical point such as cost or availability instead of embryo destruction.
Mark scheme (5 marks)
- Embryonic stem cells can differentiate into any cell type (are totipotent/pluripotent)
- Therefore embryonic stem cells could be directed to differentiate into neurones / nerve cells to replace those lost
- Adult stem cells can only differentiate into a limited range of cell types
- Therefore adult stem cells from bone marrow may not be able to differentiate into the required neurones / nerve cells
- One valid ethical issue related to using embryonic stem cells, e.g. the embryo is destroyed in the process / the embryo is a potential human life / religious or moral objections to destroying embryos
Key terms in this question
embryonic stem cells · adult stem cells
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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