Cloning Part 2 Objectives • Analyze what animals have been cloned. • Evaluate the risk of cloning. What animals have been cloned? • Scientists have been cloning animals for many years. • In 1952, the first animal, a tadpole, was cloned. • Before the creation of Dolly, the first mammal cloned from the cell of an adult animal, clones were created from embryonic cells. • Since Dolly, researchers have cloned a number of large and small animals including sheep, goats, cows, mice, pigs, cats, rabbits, and a gaur. Animals that been cloned cont. • Hundreds of cloned animals exist today, but the number of different species is limited. • Attempts at cloning certain species have been unsuccessful. • Some species may be more resistant to somatic cell nuclear transfer than others. • The process of stripping the nucleus from an egg cell and replacing it with the nucleus of a donor cell is a traumatic one, and improvements in cloning technologies may be needed before many species can be cloned successfully. Risk to Cloning • Reproductive cloning is expensive and highly inefficient. • More than 90% of cloning attempts fail to produce viable offspring. • More than 100 nuclear transfer procedures could be required to produce one viable clone. • In addition to low success rates, cloned animals tend to have more compromised immune function and higher rates of infection, tumor growth, and other disorders. Japanese studies have shown that cloned mice live in poor health and die early. Risk of Cloning Cont. • About a third of the cloned calves born alive have died young, and many of them were abnormally large. • Many cloned animals have not lived long enough to generate good data about how clones age. – Appearing healthy at a young age unfortunately is not a good indicator of long-term survival. – Clones have been known to die mysteriously. – For example, Australia's first cloned sheep appeared healthy and energetic on the day she died, and the results from her autopsy failed to determine a cause of death. Objectives • Analyze what animals have been cloned. • Evaluate the risk of cloning.