- In a multicellular organ, most cells are specialised
- However some cells remain unspecialised, these are called stem cells
- Stem cells are undifferentiatied, can keep dividing and can give rise to other cell types.
- Soon after fertilisation a zygote divides repeatedly
- These early cells are ALL stem cells, embryonic stem cells
- Theses stem cells can develop into any of the 216 cell types, they are totipotent.
- As the embryo develops many stem cells remain, these are called pluriptent. They are able to divide into any type of cell but not the cells of the placenta.
- In adults, some cells retain this ability. They can give rise to a limited number of body tissues, multipotent stem cells.
- Main source of embryonic stem cells are from unused embryos from IVF
- Adult stem cells are found in the bone marrow
- Therapeutic cloning takes the nucleus from an ovum and…