Figure 5.39: The cloning processes for reproductive and therapeutic cloning. Reproductive cloning
is used for cloning of whole organisms e.g Dolly the Sheep.- Stem cell research
Stem cells are cells found in all multicellular organisms. Stem cells can differentiate into
any type of cell such as a red blood cell, nerve cell, etc. The two types of stem cells are
embryonic stem cellsandadult stem cells. Embryonic stem cells can specialise into any
cell type, while adult stem cells usually have some restrictions as to what type of cell they
can become. Adult stem cells are produced in various tissues including the liver and the
bone marrow. Embryonic stem cells are found in the womb of pregnant animals and can
be createdin vitro(in the laboratory). Multiple embryos are generated throughin vitro
fertilisation methods. The embryos that are not implanted into a patient are frozen or stored.
Some of them are destroyed. The potential uses for stem cells include:- spinal cord injury: repairing damaged nerve tissue after paralysis
- brain damage: replacing or regenerating neurons in degenerative conditions like Parkin-
sons disease or after a stroke - cancer: creating new cells to replace cancerous cells e.g. bone marrow transplants for
people with leukaemia - burn treatment: new skin cells that match the donor may be grafted onto burn victims
Figure 5.40 shows how embryonic cells differentiate to form nerve cells.148 5.5. Applications of indigenous knowledge and biotechnology