How Human Cloning Will Work

By: Kevin Bonsor & Cristen Conger
Hello, Dolly! After Dolly was cloned in 1997, people worried that humans would be next. See more cloning pictures.
Hello, Dolly! After Dolly was cloned in 1997, people worried that humans would be next. See more cloning pictures.
Time & Life Pictures/­Getty Images

­On July 5, 1996, the most famous sheep in modern history was born. Ian Wilmut and a group of Scottish scientists announced that they had successfully cloned a sheep named Dolly.

If you stood Dolly beside a "naturally" conceived sheep, you wouldn't notice any differences between the two. In fact, to pinpoint the only major distinguishing factor between the two, you'd have to go back to the time of conception because Dolly's embryo developed without the presence of sperm. Instead, Dolly began as a cell from another sheep that was fused via electricity with a donor egg. Just one sheep -- no hanky-panky involved.


While Dolly's birth marked an incredible scientific breakthrough, it also set off questions in the scientific and global community about what -- or who -- might be next to be "duplicated." Cloning sheep and other nonhuman animals seemed more ethically benign to some than potentially cloning people. In response to such concerns in the United States, President Clinton signed a five-year moratorium on federal funding for human cloning the same year of Dolly's arrival [source: Lamb].

­Today, after more than a decade since Dolly, human cloning remains in its infancy. Although cloning technology has improved, the process still has a slim success rate of 1 to 4 percent [source: ­Burton]. That being said, science is headed in that direction -- pending governmental restraints.

Scientists have cloned a variety of animals, including mice, sheep, pigs, cows and dogs. In 2006, scientists cloned the first primate embryos of a rhesus monkey. Then, in early 2­008, the FDA officially deemed milk and meat products from cloned animals and their offspring safe to eat.

But what would human cloning involve, and how could you take sperm out of the reproductive ­equation?

Creating a Human Clone

One, two, three, clone! A simplified breakdown of how cloning works.
One, two, three, clone! A simplified breakdown of how cloning works.
© 2012 HowStuffWorks

In January 2001, a small consortium of scientists led by Panayiotis Zavos, a former University of Kentucky professor, and Italian researcher Severino Antinori said that they planned to clone a human in two years [source: Kirby]. At about the same time, news surfaced about an American couple who planned to pay $500,000 to Las Vegas-based company Clonaid for a clone of their deceased infant daughter [source: Clonaid]. Neither venture produced documented success.

Then, in 2004, South Korean scientist Hwang Woo-suk announced that he and his research team had cloned 11 human embryos for the purpose of extracting stem cells. However, after reviewing his work, a panel at Seoul National University concluded tha­t his findings were false. There ­hasn't been any confirmed human clone created to date. When discussing cloning in the sense of doing so to make a duplicate of an organism, we refer to it as reproductive cloning


­If human reproductive cloning proceeds, the primary method scientists will likely use is somatic ce­ll nuclear transfer (SCNT), which is the same procedure that was used to create Dolly the sheep. Somatic cell nuclear transfer begins when doctors take the egg from a female donor and remove its nucleus, creating an enucleated egg. A cell, which contains DNA, is taken from the person who is being cloned. Then the enucleated egg is fused together with the cloning subject's cell using electricity. This creates an embryo, which is implanted into a surrogate mother through in vitro fertilization.

If the procedure is successful, then the surrogate mother will give birth to a baby that's a clone of the cloning subject at the end of a normal gestation period. As mentioned before, the success rate for this type of procedure is small, working in only one or two out of every 100 embryos. After all, Dolly was the result of 277 previously failed attempts.

­On the surface, human cloning may evoke a similar reaction to the space program's race to the moon -- groundbreaking accomplishment, but what could we actually glean from it? Re-engineering the human reproductive process has made many people nervous that cloning crosses the ethical boundaries of science. But we can't fully evaluate the moral dilemma without first addressing the potential benefits of human cloning.

Cloning Uses

­At the outset of the clone craze, some scientists and companies focused on exploiting the science-fiction aspects of the technology. For instance, Zavos and Antinori, mentioned earlier, aimed to develop cloning to aid infertile couples -- to the tune of approximately $50,000 for the service. The group said that the procedure would involve injecting cells from an infertile male into an egg, which would be inserted into the female's uterus. This child would look the same as his or her father. Then there's the possibility of bringing deceased relatives back to life. A now-defunct company called Genetics Savings & Clone performed this type of cloning for a woman's dead cat, Little Nicky, in 2004.

­Therapeutic cloning holds the most promise of valuable medical advancement. Therapeutic cloning is the process by which a person's DNA is used to grow an embryonic clone. However, instead of inserting this embryo into a surrogate mother, its cells are used to grow stem cells. These stem cells could become the basis for customized human repair kits. They can grow replacement organs, such as hearts, livers and skin. They can also be used to grow neurons to cure those who suffer from Alzheimer's, Parkinson's or Rett syndrome. And since the stem cells would come from embryo clones using your own cell's DNA, your body would readily accept them. For more detailed information on stem cells, you can read How Stem Cells Work.


Here's how therapeutic cloning works:

  • DNA is extracted from a sick person.
  • The DNA is then inserted into an enucleated donor egg.
  • The egg then divides like a typical fertilized egg and forms an embryo.
  • Stem cells are removed from the embryo.
  • Any kind of tissue or organ can be grown from these stem cells to treat various ailments and diseases.

To clone human embryos, however, you need eggs. If therapeutic cloning were to begin in earnest, it could increase the demand for such eggs and potentially create additional moral questions regarding the donors [source: Lamb]. Speaking of ethics, there's plenty of related debate to go around when it comes to human cloning.

Human Cloning Ethics

Human reproductive cloning is banned in more than 50 countries.
Human reproductive cloning is banned in more than 50 countries.
Symphonie/Getty Images

Surveys have shown that few Americans approve of cloning for reproductive purposes, although more are open to therapeutic cloning [source: Burton]. The U.S. government has established strategic roadblocks related to human cloning, although no federal ban exists. First, the government won't fund research focused on human cloning for reproduction. Also, the FDA, which regulates public cloning research, requires anyone in the United States attempting to clone humans to first get its permission. President George W. Bush's appointed Council on Bioethics unanimously opposed cloning for reproductive purposes.

Certain countries abroad have stricter standards, and more than 50 have legally banned research efforts on reproductive human cloning [source: Medical Devices & Surgical Technology]. In Japan, human cloning is a crime punishable by up to 10 years in prison. England has allowed cloning human embryos for therapeutic use only. Many individual states have also passed laws restricting cloning.


While legal restrictions are one deterrent to pursuing human cloning at this time, some scientists believe today's technology just isn't ready to be tested on humans. Ian Wilmut, one of Dolly's co-creators, has even said that human cloning projects would be irresponsible. Cloning technology is still in its early stages, and nearly 98 percent of cloning efforts end in failure. The embryos are either not suitable for implanting into the uterus, or die some time during gestation or shortly after birth.

Those clones that do survive suffer from genetic abnormalities. Clone cells may age more rapidly, shortening their lifespan, similar to what happened with Dolly. Some clones have been born with defective hearts, lung problems, diabetes, blood vessel complications and malfunctioning immune systems. One of the more famous cases involved a cloned sheep that was born but suffered from chronic hyperventilation caused by malformed arteries leading to the lungs.


­Opponents of cloning point out that while we can euthanize defective clones of other animals, it's morally problematic if this happens during the human cloning process. Advocates of cloning respond that it's now easier to pick out defective embryos before they're implanted into the mother. In 2005, the United Nations attempted to pass a global ban on human cloning, but was unsuccessful due to disagreements over whether therapeutic cloning should be included. For now, human cloning remains in a stalemate from both a scientific and public policy perspective -- the future of human cloning will likely depend on which side gives in first.

Lots More Information

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More Great Links


  • Burton, Kelli Whitlock. "Cloning in America." GeneWatch. November/December 2005.
  • Clonaid Web site. http://ww­
  • "Cloning Fact Sheet." Human Genome Project Information. Updated July 23, 2008. (Sept. 3, 2008)
  • "Human clones: New U.N. analysis lays out world's choices." Medical Devices & Surgical Technology Week. Dec. 2, 2007.
  • Javitt, Gail H.; Suthers, Kristen; and Hudson Kathy. "Cloning: A Policy Analysis." Genetics & Public Policy Center. May 23, 2005. (Sept. 3, 2008)
  • Kirby, Alex. "Cloned human planned 'by 2003.'" BBC News. Jan. 30, 2001.
  • Lamb, Gregory M. "How Cloning Stacks Up." Christian Science Monitor. July 13, 2006. (Sept. 3, 2008)
  • "Use of Cloning Technology to Clone a Human Being." FDA. Updated Dec. 27, 2002. (Sept. 3, 2008)