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The Facts and Fiction of Cloning

Understanding the real science behind the headlines and the hubbub.

Embryo Successfully Cloned

Previous attempts to clone human embryos to obtain stem cells genetically identical to the patient are believed to have failed despite reports to the contrary -- until now.

In this new study, researchers collected 242 eggs donated by 16 South Korean volunteers. Each woman also donated some cells from her ovary.

The scientists then used a technique called somatic nuclear transfer to remove the genetic material -- which contains the nucleus of each egg -- and replace it with the nucleus from the donor's ovarian cell.

Then, using chemicals to trigger cell division, the researchers were able to create 30 blastocysts -- early-stage embryos that contain about 100 cells -- that were a genetic copy of the donor cells.

Next, the researchers harvested a single colony of stem cells that have the potential to grow into any tissue in the body. Because they are the genetic match to the donor, they aren't likely to be rejected by the patient's immune system.

"Our approach opens the door for the use of these specially developed cells in transplantation medicine," says Woo Suk Hwang, a scientist who led the research in South Korea.

Feasibility Questioned

But some researchers doubt that this technique for human cloning could ever be used for widespread treatment of disease.

"The great vision of this field is to create personalized stem cells for individual patients," says Griffin. "You'd take the cell from the patient and create the cell type you want -- say pancreatic islet cells for diabetics -- by transferring it to an egg, creating an embryo, and growing them."

"If there were enough women to donate enough eggs, and enough [funding], I'm certain it could be done," says Steven Stice, PhD, professor and GRE Eminent Scholar at the University of Georgia in Athens. "But we collect hundreds of eggs a day from cattle to do our cloning. You could never expect to do that in humans. Technically, it's not feasible."

"In the U.K., 120,000 people suffer from Parkinson's disease. Where are you going to get 120,000 human eggs? The reality is that there simply are not enough eggs ... available to make therapeutic cloning a practical, routine therapy," says Griffin.

And offering women money would still not yield the necessary numbers. The egg-harvesting process is just too uncomfortable. "Egg donation is akin to bone marrow transplantation as far as how unpleasant the process is for the donor," says Griffin.

And then there's money. "You'd have to produce an individual cell line for each person to avoid the immune response," says Stice. "The cost would be horrendous. It will be very difficult to get to an application [of the technology] that won't cost hundreds of thousands of dollars [each time]."

In the end, both experts agree that therapeutic cloning is really unnecessary, given the existing supply of viable embryos left over from in vitro fertilization. "They would be discarded," says Stice. "They're donated with consent, and would never have gone on to form an individual. There are great opportunities with existing cell lines to get to the point of treating disease. We don't have to go to [cloning]."

So why continue? Because of the wealth of information it can provide, says Griffin.

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