(Notes from the CGP revision guides)
- Cells in an early embryo can turn into any type of cell.
- A fertilized egg (zygote) divides by mitosis to produce a bundle of cells - the embryo of the new organism.
- To start with, the cells in the embryo are all the same. They're called embryonic stem cells.
- Embryonic stem cells are undifferentiated. This means they're able to divide to produce any type of specialized cell.
- In humans, all the cells in the embryo are undifferentiated up to the eight egg cell.
- The process of stem cells becoming specialized is called differentiation. As the cells start to differentiate the embryo begins to develop tissues and organs.
- All cells contain the same genes but not all genes are active in each cell type. What type of cell a stem cell differentiates into depends on what genes are active in that cell - and so what proteins that cell produces.
- Adult humans only have stem cells in certain places like bone marrow. These stem…