# 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.

> OCR A-Level Biology B — Advancing Biology (H422) — 3.1 Cell division and stem cells · Explain · 5 marks

> 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).

## Mark scheme (5 marks)

1. Stem cells are undifferentiated / unspecialised cells that can divide (by mitosis) to produce more cells
2. Stem cells can differentiate into specialised cell types / the specific type of cell needed (e.g. nerve / spinal cord cells)
3. The differentiated cells could replace the damaged cells in the spinal cord / restore normal function to the CNS
4. 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)
5. 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

- [stem cell](https://www.gradenine.co.uk/glossary/stem-cell)

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-child-is-born-with-a-36945c73) · Published by Druglandscape Ltd.