Stem Cells Characteristics They continue to grow and proliferate, Given the correct signals (from a hormone or a ‘growth factor’) they can differentiate into a particular specialized cell type

Some stem cells have more abilities than others A unipotent stem cell can form only one differentiated cell type A pluripotent stem cell can form most or all of the 210 differentiated cell types in the adult body A totipotent stem cell can form not only adult cell types, but also the specialized tissues needed for development.

Where do we get stem cells? Adult Stem Cells Skin, Sperm, Fat, Bone Embryonal Carcinoma Cells (EC cell) Embryonic Stem Cells (ES cell) Embryonic Germ Cells (EG cell)

Embryonic Stem Cells Hope A lot of cells can be grown and then given hormonal signals to specialize into a specific tissue This could be used to create new cells or tissue on demand and treat illnesses such as diabetes, Alzheimer’s and spinal cord injuries

Embryonic Stem Cells Problems Inefficient to get them to start growing and keep growing in the laboratory Hard to form the desired specific cell type in the culture dish. Could form tumors in patients Only scant evidence that embryonic stem cells can actually work in the body

Cultured embryonic stem cells Differentiation of embryonic stem cells in culture Liver cells Cultured embryonic stem cells Nerve cells Heart muscle cells Different culture conditions Different types of differentiated cells Figure 11.5

Stem Cells Donor cell Nucleus from donor cell Implant blastocyst in surrogate mother Clone of donor is born (REPRODUCTIVE cloning) Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce an early embryo (blastocyst) Remove embryonic stem cells from blastocyst and grow in culture Induce stem cells to form specialized cells for THERAPEUTIC use

Cloning Cloning means to make an identical copy of something, including copying DNA Cloning a new organism from a pre-existing one is known as asexual reproduction because it does not involve sex

How to Clone Tadpole (frog larva) Frog egg cell Nucleus UV Intestinal cell Nucleus Transplantation of nucleus Nucleus destroyed Tadpole Eight-cell embryo

Micropipette about to penetrate unfertilized sheep egg to remove nucleus Egg has been emptied of its nucleus, which holds DNA DNA from donor cell is about to enter the enucleated egg. A spark will stimulate cell divisions. Do not post to Internet

Dolly, the first cloned sheep, with her lamb Do not post to Internet

Click to view animation. Cloning of Dolly Click to view animation.