Stem cells, unlike other cell types, are unspecialized cells that can use cell division to renew themselves even after long periods of not being active and under certain conditions, can become tissue or organ-specific cells developed to perform certain functions and can develop into many different types of the cell. The two main types of stem cells that have been used are embryonic stem cells and non-embryonic somatic (adult) cells. Stem cells offer a possibility for treating diseases like diabetes or heart diseases and the blood-forming stem cells (hematopoietic stem cells) currently used to help in the rebuilding of the immune system after leukemia or other autoimmune disorders.

Gene Therapy is the correction of defective genes that are the causes of diseases, such as heredity diseases, through the replacement of a defective gene with a normal one, through homologous recombination, or regulation of turning on or off a particular gene. Gene Therapy can be classified into germ line therapy and somatic gene therapy.

Germ line Therapy

Germ cells are modified by the insertion of functional genes into the genomes of the patients to be passed on to later generation and is highly effective in fixing genetic disorder or hereditary diseases that may be passed on but this is currently considered illegal for the application in human beings for various technical and ethical reasons.

Somatic Gene Therapy

Therapeutic genes are transferred into the somatic gene and any effects or changes are restricted and will not be passed on to the next generation. This is still illegal in the UK because of consideration of the next generation.