Stem cells are special types of cells that provide tissue renewal and may be used to grow tissue or organ replacements. Stem cells can be isolated from blood, brain or muscle tissue, but can now also be cultured from early human embryos. Further developments in stem cell culture techniques are likely to pave the way for the growth of tissues or organs for transplantation and new treatments for serious illnesses such as Parkinson's, Huntington's, Alzheimer's and certain types of cancer. Cloning Cloning is a word that is used in different ways by different people. This tends to create confusion in discussions about cloning.
Scientists say they clone DNA when they reproduce DNA for routine research purposes.
Home gardeners clone plants when they take cuttings to grow a new plant. Tissues and organs are said to be cloned when they are reproduced for research or medical purposes. In the last few years, newer techniques of cloning have been developed which allow a whole organism, like an animal, to be reproduced asexually from a single cell. This was the technique used to clone Dolly the sheep. The possibility of human reproduction through cloning raises many ethical concerns and the technique is unlikely to be permitted by nations in the foreseeable future.