"How is a sheep just like a carrot?" Professor Rachel Fink asked her introductory biology students the day after learning that Scottish scientists had cloned a sheep. Her colleague Diana Stein, who coteaches the course, had opened the semester by stating that plant cells can be cloned since any plant cell can give rise to every type of cell needed to make a plant. This isn't true for animals, or so scientists believed, until "Dolly" proved that sheep, like carrots, can be cloned.
Dolly wasn't the first cloned mammal, but she was the first cloned from an adult animal cell. It was previously believed that once a cell differentiated and found a "career" as a muscle or brain cell, for example, there was no way to change its destiny. Dolly's cloning proved that assumption wrong. By putting differentiated cells into a resting state, researchers were apparently able to "reprogram" them for other roles in the sheep's development.
Developmental biologist Craig Woodard believes cloning should interest everyone, not just biologists. "I want people to educate themselves about cloning, because more and more we will be able to manipulate the genes of living things, and this will affect us all profoundly," he says. To go beyond the headlines, Fink recommends reading the February 27 issue of Nature, in which the cloning research was originally published, or the March 7 issue of Science, which has an articulate yet accessible analysis of the scientific and ethical issues involved. "Society must catch up with the scientists," says Fink. "Laypeople should read about cloning because it's exciting and because someday it may directly affect your life." If that seems far-fetched, consider how quickly in vitro fertilization moved from theory to reality.
Fink's research isn't on cloning, but she studies a related issue: how cells specialize. Woodard also asks basic questions about animal development, studying how genes direct the development of fruit flies. Woodard says the cloning breakthrough is valuable to basic researchers. "By learning more about how it happened, we can learn what makes cells differentiate and what state a cell must be in not to become restricted to one fate only. These are key questions for developmental biologists."
Since sheep can be cloned, are cloned people next? Fink says that since "every animal jump-starts a fertilized egg differently," what's possible in a sheep may not be possible in humans. "Since it won't be practical to clone people soon, to ban research into human cloning would mean losing valuable information about embryology," she says. "We can't learn all we need to know about human disease and development using mice." Woodard supports the ban on human cloning research, but favors animal cloning. "If cloning can benefit humans significantly and can help us answer basic questions about how animals develop, it's a good thing to do," he says.
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