Researchers Successfully Clone Sheep -- Creating Copies Of Humans Could Be Possible
Scottish researchers have broken one of nature's greatest taboos by cloning a lamb from a single cell of an adult animal, a breakthrough that opens the door to the possibility of cloning humans.
Although the remarkable achievement is being hailed as a potentially great advance in animal agriculture, it could create an ethical quagmire about its use in humans.
The first report of cloning a mammal - making a genetically identical copy from a single body cell - appears in the Feb. 27 issue of the British science journal Nature.
Researchers headed by Ian Wilmut of the Roslin Institute in Midlothian, Scotland, showed that a fully differentiated cell from the mammary tissue of a ewe could be manipulated in such a way as to create a genetically identical copy of the animal it was taken from.
Scientists have long believed that once a cell became differentiated, most of its approximately 100,000 genes were permanently shut off. Only a few genes remained active to permit the cell to perform its specific function, whether that is to produce milk, hair or organ tissue.
All previous efforts to reactivate the shut-off genes had failed. English researchers came the closest by coaxing frog body cells to develop into tadpoles. They never, however, went on to become frogs.
The Scottish scientists had many failures with the sheep cells before their first success, but the fact that it was accomplished with a mammal means that other mammals, including humans, could possibly be cloned.
Exactly how the technique works is unclear. But the scientists speculate that by making the mammary cells dormant and bringing them close to the point of death, something happens to break the chemical locks that have kept most of the genes inoperative.
The mammary cell is then inserted into an unfertilized sheep egg cell that has had its own genetic material removed. Fusing the cells tricks the egg cell into thinking it has become fertilized.
Then, the researchers think, the chemical machinery inside the egg cell goes to work to reprogram the mammary-cell genes into starting all over again, as if they were for the first time brought together as sperm and egg. The cell divides, produces an embryo, fetus and newborn that grows into a mirror image of its adult donor.
The results of the cloning research had been embargoed by the journal Nature until Wednesday. But the Reuters news agency, quoting an author of the study, reported details yesterday.
Although the U.S. government prohibits government dollars from being spent on human cloning research and ethicists decry it, nevertheless it could be done, said Neal First, professor of animal biotechnology and reproductive biology at the University of Wisconsin.
First said that in the United States there are no laws banning human cloning research, as there are in some European countries.
Thus, if a wealthy person wanted to clone himself, theoretically it could be done, he said.
"A private clinic could set up and clone that person just as nice as could be. There are no rules or restrictions preventing it," he said.
The National Advisory Board on Ethics in Reproduction, which is supported by federal and private money, studied human cloning and concluded that it had no merit for human society, said First, a member of the board.
Basically there are no good reasons to clone humans. A duplicate body does not mean a duplicate person. The clone's brain would be far different from that of the donor, as it must start from scratch and build its own world of experiences. A cloned Hitler, for example, might turn out to be a philanthropist.
But cloning's potential for agriculture could be far greater than any other technology so far developed, First said.
"If the technique is made efficient, it has the potential for really revolutionizing what we do in animal breeding," he said.
Cloning the best milk producers could reduce the nation's dairy herd by a third, cut food costs and help protect the environment. But dairy farmers probably wouldn't like it, First said, because many would go out of business.
"That gets to be a social issue . . ." he said.
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