REVIEW • Asexual cloning occurs in nature • Plants and less complex organisms can all duplicate trough asexual methods • Complex, multicellular organisms have lost ability to asexually reproduce • Cells have become too specialized
Human Assisted Cloning Can be used to save the DNA from endangered species or mass produce organisms with desirable traits There are two types of cloning we’ll discuss: Reproduction Cloning Therapeutic Cloning
Reproductive Cloning Also called adult DNA cloning Purpose: to create a genetic duplicate of an existing (or previously existing) organism with desirable traits Because the cells are specialized, you can’t just turn a single skin cell into a new individual!
Dolly, the World’s Most Famous Cloned Sheep July 5, 1996 – Feb. 14, 2003 cloned from the cell of a mammary gland Was able to reproduce
How did they do it? There are 5 steps in the therapeutic cloning process: Remove nucleus from an egg cell A mammary gland cell is removedfrom an adult female Electricity fuses mammary and egg cell Fused cell begins dividing Dividing embryo is inserted intosurrogate mother
Problems Scientists Encountered only about 10% of clones usually survive Surviving clones can be abnormally large and experience higher rates of infection and cancer For example, before Dolly died of a lung disease she appeared to be aging faster than other sheep.
Therapeutic Cloning used to correct health problems uses human embryonic stem cellsand adult stem cells Stem Cells: cells that have the potential to become many different types of cells Embryonic Stem Cells: more desirable because they can become any one of our 200 types of body cells
Stem cells can be used to replace damaged cells in patients with diabetes, spinal cord injuries, and Parkinson’s disease. Embryonic stem cells are often used Adult stem cells are not as adaptable
Adult stem cells form bone marrow have been used in transplants for 30 years • Have recently been used to regenerate nerves and heart tissue, and to treat diabetes • Controversial because the best stem cells are from embryos which are destroyed when harvesting cells