By Daniel Denoon Webmd Feature

By Daniel DeNoon WebMD Feature

Reviewed By Michael Smith

As cloning claims continue to be made, science gets lost in the shuffle. WebMD has answers to your questions about cloning.

What is a clone?

It all starts with genes. A normal baby gets one set of genes from its mother's egg and another set from its father's sperm. When an egg is fertilized, these two sets of genes combine and the egg becomes a zygote. The zygote divides over and over again to form an embryo. The embryo attaches to the womb, becomes a fetus, and is born into the world as a brand new baby. In the center -- the nucleus -- of each of its cells, it carries that same mixed pair of genes -- the genes from the mother and the father.

Like a normal baby, a clone starts with an egg. But in this case, the genes are taken out of the egg and replaced with the nucleus (genetic material) of an adult cell. A jolt of electricity fuses the new genes to the egg, making it a clonal zygote. By a process not yet understood, the adult genes get reprogrammed to begin life all over again. The clonal zygote develops into a clonal embryo.

At this point, cloning can take two different paths. For therapeutic cloning, the clonal embryo is allowed to divide into a number of premature cells called stem cells. These stem cells have the ability to grow into any kind of cell. They could theoretically be used to replace damaged or diseased cells in the person who donated the genetic material. Since they would be identical to the donor's own cells, they would not be rejected.

For reproductive cloning, the clonal embryo would have to be implanted into a woman's womb. If all went well, the clonal embryo would become a clonal baby. This baby would have exactly the same genes as the person who donated the genetic material from his or her adult cell. That means the baby would be an exact genetic copy of the donor -- the nuclear donor's clone.

Who are a clone's biological mother and father?

Biological mothers and fathers make babies by sexual reproduction. Cloning is asexual reproduction. A cloned baby wouldn't have biological parents. It would have a single donor of genetic material.

If a person were cloned, would the clone be that person's child or sibling?

No. It would not be a daughter or son, sister, or brother. It would be a brand-new kind of human relationship: a clone.

Would a clone be an exact copy of the person who was cloned?

The clone would have the same genes as the donor of the genetic material. But genes aren't the only things that make people who they are. Experience, environment, education, and temperament all exert strong effects. Most of us have met identical twins. Like clones, identical twins have exactly the same genes. They look a lot alike, but once you get to know them it's easy to tell them apart. They are different people. And twins usually are raised together. A clone would have a totally different upbringing than the person whose genes it carried.

Could you clone another Hitler?

If cells from Hitler's body somehow were preserved with their DNA intact, it would be a remote possibility. But the cloned baby would have a much different experience and environment. It would be a different person.

Are clones instant adults?

No. Clones start as babies. Cloned baby animals take just as long to grow up as normal baby animals.

Has someone really cloned a person? Is it possible?

Animals have been cloned. But it takes a lot of effort. Most cloning attempts fail. Researchers go through a lot of eggs before they can get one to fuse with donor DNA. Getting eggs from humans, as any woman who has gone through in vitro fertilization will attest, is neither easy nor painless. Many researchers feel it would be unethical to put a woman through this process in order to create a human clone. Cloning experiments on human cells so far have used extra eggs donated by women who underwent in vitro fertilization.

A major problem with human cloning is that cloning techniques now are quite primitive. Cloned animals often have genetic defects. Dolly the cloned sheep is obese. Molly the cloned cow dropped dead.

The Raelian cult claims to have cloned human babies. There's no proof at all that they have done so, and scientists are very skeptical. Severino Antinori, MD, an Italian fertility specialist, claims he has cloned a human embryo that will be born in January. Panos Zavos, PhD, the owner of a Kentucky fertility clinic, also claims to be close to human cloning. These claims, too, are met with a high level of skepticism.

But given enough time and persistence, it's possible -- maybe inevitable -- that someone will produce a human clone.

What is the difference between test-tube babies and clones?

So-called "test-tube" babies come from in vitro fertilization. The process is used to help people with fertility problems have biological children. As in cloning, eggs are taken from a woman's ovaries. They keep their genetic material intact. These eggs are mixed with sperm from the biological father in the laboratory -- in the "test tube." Once fertilized, the eggs grow into embryos and are placed into a woman's womb -- and must implant into the uterus to survive. The resulting embryos have one set of genes from the woman who donated the egg, and another set from the man who donated the sperm. They are not clones.

Is cloning legal?

The U.S. now has no specific law against cloning. However, several states have enacted such laws. Meanwhile, the U.S. FDA has warned researchers that any human reproductive cloning would be an experiment needing FDA approval. Such approval, it states, will not be forthcoming.

Is cloning ethical?

Some experts say that people should have reproductive freedom -- and that this freedom extends to cloning. Most ethicists and researchers contacted who spoke with WebMD over the course of the past three years draw a line. Many support therapeutic cloning, in which the cloned embryo is never implanted into a womb and in which no baby is actually cloned. Nearly all oppose reproductive cloning. Both the National Academy of Sciences and the American Society for Reproductive Medicine have strongly stated that they oppose reproductive cloning.

Published Jan. 6, 2003.

SOURCES: "Human Cloning and Genetic Modification," Association of Reproductive Health Professionals web site ( FDA ( American Society for Reproductive Medicine ( National Academy of Sciences web site ( WebMD Medical News: "Cloning Goes to Washington" ( WebMD Medical News: "Cloning with Adult Cells Is Possible" ( WebMD Medical News: "Cloned Animals Have Abnormal Genes" ( WebMD Medical News: "New Year May Welcome a Cloned Baby."