Dolly: a hard act to follow

[摘要] After the birth of Dolly; the first mammal ever to be cloned; in 1997, many scientists believed that in a few years they would understand the magic in the egg that allows it to reprogramme a cell's DNA. After Dolly, scientists thought they would soon be able to clone many other mammals. Scientists have made some progress towards potential applications. For instance, they have cloned transgenic pigs that might one day be used as organ donors, transgenic cows and goats that produce proteins that some humans lack. But the low efficiency of the cloning process has stymied industrial development, and most companies set up to commercialize cloning have shut down.