A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
There are two main types of stem cells:
Adult stem cells - found in the bone marrow can form many types of cells including blood cells.
Embryonic stem cells - stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
Treatment with stem cells may be able to help conditions such as diabetes and paralysis.
Plants also have stem cells, meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
Uses of cloning
In therapeutic cloning an embry os produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient's body so they may be used for medical treatment.
The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objectives.
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically. This means that:
- Rare species can be bloned to protect from extinction
- Crop plants with special features (such as disease resistance) can be cloned to produce large numbers of identical plants for farmers.