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Year in Review: 1997

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Princess Diana's death stuns the world

Weld steps out -
Cellucci steps forward

Mother Teresa is laid
to rest at age 87

Chinese rule returns
to Hong Kong

Supreme Court strikes
down 'Net decency act

UPS strike disrupts thousands of firms

Heaven's Gate cult commits mass suicide

Mars Pathfinder explores Red Planet

Ellen comes out, marking a first in TV

For the first time, a mammal is cloned


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Cloning of adult mammal breaks the scientific mold

By Richard Saltus, Globe Staff, 02/24/97

The world's first clone of an adult animal, Dolly a seven-month-old sheep, stands in her pen at the Roslin Institute in Edinburgh, February 23. Dr Ian Wilmut and his team of genetic scientists took one cell from a sheep's udder from which they created a viable embryo, which in turn was successfully implanted in a surrogate mother and brought to full term. (Reuters Photo) The world's first clone of an adult animal, Dolly, a seven-month-old sheep, stands in her pen at the Roslin Institute in Edinburgh, February 23. (Reuters File Photo)

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Medical, ethical questions posed

Views split on ability to
clone humans

Roslin Institute Web site


Scientists say they have created the first clone, or genetically identical copy, of an adult mammal in a feat that not only would disprove longstanding biological dogma but also raise eerie possibilities of copying human beings.

The Scottish researchers appear to have breached what had been thought an insurmountable barrier: reproducing a grown mammal by taking genes from one of its cells and creating a new embryo that would develop into the donor's duplicate.

The report yesterday from Edinburgh immediately resurrected the controversy over potentially cloning humans that last surfaced in 1993, when US researchers said they had created identical copies of human embryos.

Those identical embryos were not viable, and the experiments were discontinued. Critics feared that the technique might be used to create twins or greater numbers of copies of an embryo, but in any case it wouldn't have made it possible to copy a matured human.

That is what scientists yesterday said was so stunning about the research at Roslin Institute in Midlothian, Scotland, where researcher Ian Wilmut and his colleagues created Dolly, a sheep now 7 months old that was generated from mammary cells of a fully grown ewe.

They said they devised a way to use the genetic blueprints inside a single adult cell to create a new individual with its panoply of differing cells, tissues, and organs. And they said it could be used to make unlimited numbers of identical clones.

"It's very exciting, it's something we never thought we could do," said Karl Ebert, a researcher at the Tufts School of Veterinary Medicine who was not involved in the experiment but said he was "trying to break into it myself" as a way of duplicating genetically altered farm animals. Ebert heads a company called Midas Biologicals of Grafton, which is involved in putting genes for various pharmaceutical substances into goats, which then secrete the products in their milk.

The Scottish result, which is to be reported later this week in the journal Nature, doesn't guarantee that human adults could be similarly copied. But the report inevitably raised the specter of producing human copies by the tens or thousands, of workers or soldiers, Hitlers or Einsteins, or even a replacement for a couple's child who died tragically young.

"I don't think anybody is likely to use it in humans," said Dr. Ralph Brinster of the University of Pennsylvania School of Medicine in a telephone interview. Brinster, who pioneered the creation of animals with altered genes, said he did not believe the new method would be "technically feasible" in humans but did not elaborate.

News reports from Britain yesterday described in general the novel method used to clone the adult sheep.

They first removed single cells from the udder of the ewe. For reasons not immediately clear, the mammary cells appeared to be particularly effective in the experiment.

The researchers next extracted just the nucleus -- the central part of the cell that contains the chromosomes that carry the animal's genes. These are all the genes necessary to create an individual. However, in adult cells of animals and humans, only some of the millions of genes are usually functioning, and the rest, it was thought, were "turned off" once the individual was fully grown.

The scientists then soaked the nuclei in chemicals that made the genetic material temporarily inactive.

Next, they combined the nucleus with an unfertilized egg that had been stripped of its own genetic material, producing an embryo whose development would be guided only by the chromosomes and genes from the ewe's mammary cell.

This was the crux and most dramatic part of the experiment. Cells in adult animals or humans are almost all "committed" to a particular role -- as a skin cell or bone cell or nerve cell -- and all other genes not necessary for this role are inactive. Somehow, the scientists' method enables the nucleus' full set of genes to become active, guiding the development of the embryo into a complete and normal baby sheep.

The embryo was implanted into the womb of a surrogate mother sheep, which gave birth to Dolly last July.

Brinster said that while the achievement was a milestone, he was not totally surprised that it proved possible.

Even though genes are turned off in adult cells, he noted, "there's no evidence to indicate that that DNA is lost: It doesn't mean the [genetic] code is gone -- the code is still there." But it took the specific manipulations of the Scottish team to enable the nucleus to "be reprogrammed" after it was placed in the unfertilized egg, and subsequently generate a new, full-fledged animal, he said.

Dr. George Annas, professor of health law at Boston University School of Medicine, said he thought the new method, if possible on a large scale, would be used mainly to reproduce outstanding farm animals or to copy genetically altered animals.

Even if human beings could be cloned, he said, it would be decades before the copy of an adult human reached that person's age, making it a very inefficient strategy.

"I suppose it could provide some sort of immortality if you wanted to live forever," said Annas in an interview. "But it would only create a physically identical copy of yourself" that might grow up with a different personality due to effects of the environment and emotional experience, he said.

As for the ethics or legality of human cloning, said Annas, "So far we have a lot of ethical statements that it shouldn't be done, but no law prohibiting it."

Science fiction writers have speculated that if a living adult animal could be cloned, perhaps dead or even extinct ones could, too. That was the premise of the book and movie "Jurassic Park," in which living dinosaurs were generated from ancient DNA that had been extracted from amber. But Brinster said he thought such a scenario would not be possible despite the success of the sheep experiment.


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