2. Stem Cells? Two main characteristics - unspecialized cells that renew themselves for long periods of time - they can be induced to become cells with special functions Importance - in the developing fetus, stem cells give rise to multiple specialized cell types ex. Cells that create heart, lung, and skin tissue - in some adult tissues, stem cells manifest replacements for dead cells ex. Bone marrow, muscles, brain

3. Embryonic Stem Cells Derived - from embryos that develop from eggs that have been fertilized artificially - they are not derived from eggs fertilized in a woman's body. - the embryos from which human embryonic stem cells are derived are typically four or five days old

4. Adult Stem Cells Abilities - renewal - can differentiate to make major specialized cells ex. For tissues or organs Where - stem cells are thought to reside in a specific area of each tissue where they may remain non-dividing for an extended period of time until they are activated by disease or tissue injury

5. Contrast - embryonic stem cells can become all cell types of the body - adult stem cells are generally limited to differentiating into different cell types of their tissue - large numbers of embryonic stem cells can be relatively easily grown in culture, while adult stem cells are rarer and methods to harvest them are still being experimented - adult stem cells can be removed from the patient, harvested, then reintroduced into the body, theoretically not causing rejection by the immune system - embryonic stem cells could be rejected by the immune system, but it has never been tested in humans

6. Applications Apps - new therapies and plans of attacks against disease ex. Cancer, Parkinsin’s, Alzheimer's - test new drugs - could be used in place of transplanting organs/tissue