来源：未知 | 点击量：次
Why do some people want to clone?
Our experiences have told us that, with a little work, we humans can clone just about anything we want, from frogs to sheep—and probably even ourselves.
So we can clone things. But why would we want to? Below are some of the ways in which cloning might be useful.
Cloning animal models of disease.Much of what researchers learn about human disease comes from studying animal models such as mice. Often, animal models are genetically engineered to carry disease-causing mutations in their genes. Creating these transgenic animals is a time-intensive process that requires trial-and-error and several generations of breeding. Cloning could help reduce the time needed to make a transgenic animal model, and the result would be a population of genetically identical animals for study.
Cloning endangered species is much easier, mainly because the surviving animals can donate healthy, living cells. In fact, several wild species have been cloned already, including two relatives of cattle called the guar and the banteng, mouflon sheep, deer, bison, and coyotes. However, some experts are skeptical that cloning can help a species recover. One big challenge endangered species face is the loss of genetic diversity, and cloning does nothing to address this problem. When a species has high genetic diversity, there is a better chance that some individuals would have genetic variations that could help them survive an environmental challenge such as an infectious disease. Cloning also does not address the problems that put the species in danger in the first place, such as habitat destruction and hunting. But cloning may be one more tool that conservation scientists can add to their toolbox.
Farm animals such as cows, sheep, and goats are being genetically enngineered to produce drugs or proteins that are useful in medicine. As an example, scientists could take cells from a cow that produces large amounts of milk and grow them in culture. Then they could insert a gene into the DNA of these cells that codes for a drug or a vaccine. If they take the nucleus from one of these cells and transfer it to a cow egg, it could develop into a cow that makes the drug in its milk. Since every cell in the cow would carry the drug gene, it could pass the gene to its offspring, creating a whole herd of drug-producing cows. Even better, we could avoid the issue of the genetic reshuffling that happensduring sexual reproduction and simply clone our drug-producing cow.