2. Induced Pluripotent Stem Cells iPS cells Are adult cells Does not require eggs or embryos Easy to make Still don’t know if these differ from embryonic stem cells Express stem cell markers Can generate all three germ layers Useful tools in drug development Hope to be used in transplantation medicine Tissues will be almost an identical match to cell donor, so rejection is unlikely

3. Adult Stem Cells Referred to as somatic stem cells Thought to be undifferentiated Found among differentiated cells in tissues and organs Can renew itself and can yield some or all specialized cell types of the tissue or organ Origin is still unknown in mature tissues Found in many tissues including the brain and heart, and other areas like peripheral blood, blood vessels, skeletal muscle, skin, teeth, gut, liver, and testis In each tissue there is limited numbers of adult stem cells Once removed from the body, the ability to divide is limited It is tough to obtain large quantities of the stem cells Have the ability to divide, and give rise to mature cell types that have characteristic shapes and specialized structures and functions of a particular tissue.

4. Embryonic Stem Cells Come from embryos Most come from embryos that develop from eggs that have been fertilized invitro Donated to research NOT derived from eggs fertilized in a woman’s body. The embryos are typically four to five days old and are a hollow microscopic ball of cells called a blastocyst Are isolated by transferring the inner cell mass into a culture dish that contains nutrients The cells will divide and spread over around the dish Process in generating these is inefficient, so the lines are not produced If the icm does survive, divide, and multiply then they are removed and placed into new culture dishes Once the cell line is established, the original cells and yield millions of embryonic stem cells These cells can be frozen and shipped around to other laboratories