# A scientist is comparing embryonic stem cells and adult stem cells for use in treating patients with blood disorders such as leukaemia. Explain the differences between embryonic stem cells and adult stem cells, and suggest why adult stem cells found in bone marrow are particularly useful for treating blood disorders.

> OCR A-Level Biology B — Advancing Biology (H422) — 2.2 Biological molecules including biochemistry · Explain · 5 marks

> Leukaemia is a cancer in which the bone marrow produces abnormal white blood cells. One treatment involves replacing the patient's bone marrow with healthy donor bone marrow containing stem cells, which then produce normal blood cells.

## Mark scheme (5 marks)

1. Embryonic stem cells can differentiate into any cell type (they are pluripotent / totipotent)
2. Adult stem cells can only differentiate into many (but not all) cell types / a more limited range of cell types than embryonic stem cells
3. Adult stem cells are found in bone marrow (whereas embryonic stem cells are found in early embryos)
4. Bone marrow contains stem cells that can develop into red blood cells (and white blood cells / blood cells), making them directly useful for replacing abnormal blood cells in leukaemia
5. Using embryonic stem cells raises ethical issues (e.g. the embryo is destroyed) whereas adult stem cells do not raise the same ethical concerns / adult stem cells can be taken from the patient or a donor without destroying an embryo

## Key terms

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

## 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-scientist-is-comparing-embryonic-stem-2c3d3015) · Published by Druglandscape Ltd.