Human Cloning May Be Just Around the Corner

Dolly the sheep and her first-born lamb, Bonnie.

Dolly the sheep and her first-born lamb, Bonnie. Roslin Institute hide caption

itoggle caption Roslin Institute

Q&A: What We've Learned About Cloning

  

Animal cloning has seen significant advances, to the point where the FDA has declared cloned meat safe. But pet cloning has turned out to be a bust. Find out why.

South Korean researchers claimed this image showed a cloned human embryo used to generate stem cells

South Korean researchers claimed this image showed a cloned human embryo used to generate stem cells. Their report proved to be fraudulent. Seoul National University/Getty Images hide caption

itoggle caption Seoul National University/Getty Images

Ten years ago Thursday, the public learned that Scottish scientists had cloned a sheep.

Dolly was the world's first cloned mammal. The news brought often hysterical speculation that human cloning was just around the corner. Today, human cloning may indeed be just around the corner, but not in the way people feared a decade ago.

Each one of a person's skin cells contains all the DNA necessary to make that person. But because it's a skin cell, the DNA has undergone some physical changes. These changes have the effect of turning off lots of genes that aren't needed for making a person's skin. The same is true for virtually all the cells in a human body.

The Roslin Institute scientists showed that it was possible to undo those changes by putting a cell into an egg. Somehow, the egg is able to rejuvenate the DNA. It restores the potential of any adult cell's DNA to make an entire animal.

That's how Dolly was made, and the technique took off.

Despite all the success with four-legged animals, there were no credible reports suggesting human cloning was possible — until 2004, when South Koreans claimed they had successfully cloned a human embryo.

The claim appeared in the prestigious journal Science, but the report turned out to be fraudulent.

The Korean scientists weren't trying to make a cloned baby. They were trying to make a cloned embryo in order make embryonic stem cells.

Here's why: If a skin cell is used to make a cloned embryo, any stem cells from that embryo would be genetically identical to the person who provided the skin cell. And thus, that person's immune system wouldn't reject tissue grown from those stem cells.

This promise of tailor-made stem-cell therapies has prompted several teams of scientists around the world to try to make embryonic stem cells from cloned embryos. But Robert Lanza of the biotech firm ACT says no one's managed it — yet.

"There have now been at least a dozen ... species cloned, but for each species there's been a unique set of problems, and the human is no different," Lanza says.

One reason the roadblocks to human cloning are hard to overcome is the shortage of human eggs for research.

Robert Blelloch of the University of California San Francisco says that made him decide to begin his work on human cloning by studying monkeys first.

"If we can figure out these big roadblocks in a system where we have better access to healthy eggs, then I think we'll be in a much better position," Blelloch says. "Once we figure those roadblocks out, we can move on to humans."

Another hurdle is ignorance about precisely how a fertilized egg begins to divide and grow.

"Because the federal government has prohibited academic institutions from working on embryos, we really know almost nothing about human embryos in the beginning stages," says Susan Fisher, a stem-cell scientist at UC San Francisco.

The opportunities for gaining that knowledge are probably greatest in California, where Fisher and Blelloch work, because California has committed to spending $3 billion on cloning and stem-cell research over the next decade.

"So for us to get somewhere, I really think that we need to understand the basic biology. Otherwise, we are just technicians who are trying a whole bunch of things, and there's so much to try," Fisher says.

Despite the hurdles, Fisher, Blelloch and Lanza don't hesitate when asked whether someone will succeed in cloning a human embryo.

"Oh, I absolutely do think it's going to happen," Fisher says. "I don't think there's any biological reason why the human is any different than other mammalian species."

Of course, while it may be technically possible to make a cloned human embryo, President Bush and others have argued it's morally wrong — and not something scientists should do.

Cloning Q&A: What Have We Learned Since Dolly?

Ten years ago, Scottish scientists proved an animal could be cloned — and raised a burning question: Would a human be next?

Before Dolly the cloned sheep, who was euthanized at age 6 due to a lung infection, scientists had been trying for decades to make a clone, or genetic copy, of an animal. To make a clone, a nucleus is removed from an egg and replaced with the nucleus of a cell from the animal to be cloned. The egg is then coaxed to begin dividing. After a few divisions, the cloned embryo can either be transferred to a uterus, or used to derive embryonic stem cells.

Ethical and technical roadblocks to cloning a human embryo remain substantial. At the same time, scientists have made significant advances in cloning animals. Here, a look at cloning developments since Dolly's birth:

Q: In the decade since Dolly was revealed to the world, what practical advances in cloning have been made?

Although cloning still is not an efficient process, scientists have become more efficient at making cloned animals. It still requires dozens, if not hundreds, of fresh eggs to make a cloned embryo, and then only a small fraction of the cloned embryos will produce a live birth after being transferred to an animal's womb.

But the process is efficient enough to make it possible to clone prized barnyard animals for breeding stock, and it may be possible to insert genes into these animals that will give them desirable traits. For example, scientists have inserted a gene into pigs that causes them to produce a kind of fat that is healthier for the human diet. That gene is also passed onto to the clone's offspring, which means whole herds of an animal containing a desirable trait could be created.

Q: Why no announcement of a human clone?

No reputable scientist is attempting to clone a live human being. That said, several teams around the world are trying to make cloned human embryos with the intention of deriving embryonic stem cells. No one has succeeded yet. A South Koren lab's claim to have done that turned out to be fraudulent.

Some species are harder to clone than others. Primates, including humans, have proven especially difficult. At least part of the problem is the scarcity of eggs needed to initiate the cloning process.

Q: Does cloning have the potential to improve our lives?

Cloning animals is an important research tool, because it provides a way of creating animals with desirable traits. This is significant for agriculturally important livestock.

As far as human cloning is concerned, scientists see two primary reasons to make embryonic stem cells from cloned embryos. One, stem cells made from an individual will not be rejected if they are transferred back to that individual in some future therapy. Two, it would be possible to make stem-cell lines from people with specific diseases, thus creating a new way of studying those diseases in cells grown in the laboratory.

Q: Are the ethical issues still the same?

There's still no question that most people consider attempting to clone a human being unethical — at the very least because the cloning process seems to create animals with health problems.

For people opposed to destroying human embryos for any reason, cloned embryos present an ethical dilemma: Since a cloned embryo is a potential human life, it's wrong to destroy it. But those opposed also believe it's wrong to make a cloned human being, so the embryo shouldn't be implanted in a woman, either.

Q: What steps have been taken to prevent the creation of human clones?

In the United States, no steps have been taken to prevent the cloning of a human being. All attempts to legislate on this issue have bogged down, because opponents of cloning want to ban all cloning, whereas scientists say creating embryos and stem cells would be valuable for research. Most other countries in the world do have laws banning so-called reproductive cloning; some also ban all forms of cloning as well.

Q: Has cloning had any impact yet on the average person's life?

No. There are livestock husbandry companies that are hoping to make money by cloning prized animals. Companies offering to clone prized pets have gone out of business.

The FDA has declared meat from cloned animals and their offspring safe to eat, but the agency has asked that businesses not yet put these products on the market. Nor is it yet economically feasible to sell cloned meat; clones are still very expensive to make.

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