Stem Cells Untapped and unproven potential for treating human conditions Characteristics: capable of self renewal and differentiation Stem cell divides (mitosis) stem cell + progenitor cell Progenitor cell (partially specialized) Terms of Potential: Totipotent: daughter cells that can specialize as any cell type Pluripotent: daughter cells that can specialize as any of a restricted number of cell types (progenitor cells) Stem Cells From Embryos: (Ethical Objections) Embryos from couples of IVF (frozen “extras”); cells removed from blastocyst cultured in flasks Avoid aging (senescence) with high level of telomerase

Amniotic Fluid: derived stem cells can become neurons, bone, blood vessels, liver cells Somatic Cell Nuclear Transfer: Patient’s somatic cell nucleus injected into donated egg cell (therapeutic cloning) Ethical issues with embryos: 50-60% morally acceptable Stem Cells From Adults: Hematopoietic stem cells from bone marrow transplants Drugs to treat breast cancer; “heart patches” from transplants, leukemia treatments Nuclear Reprograming for Producing Pluripotent Stem Cells  Take a differentiated adult cell and alter its patterns of gene expression to reprogram the cell to an early stage in its differentiation pathway (undifferentiated pluripotent state)  Low viability  Shown to form tumors