A level Biology B · Edexcel 9BI0 · Topic 7C
Stem cells
Key points
- Stem cells are undifferentiated cells that can divide repeatedly and differentiate into specialised cells.
- Totipotent cells (early embryo) can form any cell, including placenta; pluripotent cells (embryonic stem cells) can form any body cell; multipotent cells (adult stem cells, e.g. bone marrow) form a limited range.
- Differentiation happens because different genes are switched on or off, so different proteins are made.
- Induced pluripotent stem cells (iPS cells) are made by reprogramming adult cells using transcription factors.
- Uses include treating leukaemia (bone marrow transplants), possible repair of damaged tissue and testing drugs.
- Ethical issues: embryonic stem cell use destroys embryos; regulatory bodies decide what research is allowed.
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Stem cells are unspecialised cells that can keep dividing and can differentiate into specialised cells. They hold great promise for medicine, but the most versatile ones come from embryos, which raises ethical questions.
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