A team of South Korean scientists led by the Hwang Woo-suk – who made headlines in 2005 for falsely claiming to have extracted stem cells from cloned human embryos – has just announced that they have successfully cloned coyotes for the first time. Here are some answers to a few questions you may have about reproductive cloning.
How does reproductive cloning work?
Reproductive cloning usually employs a technique called somatic cell nuclear transfer. Researchers first take a somatic cell (any cell in the body other than a sperm or egg) from the creature they plan to clone, extract the cell's nucleus, which contains the cell's nuclear DNA, and discard the rest. They then remove the nucleus of an egg cell and insert the somatic cell nucleus in its place. Next, they treat the reconstructed egg with chemicals or electricity to stimulate cell division. If the egg divides normally and forms a blastocyst (a small clump of cells that forms after an egg is fertilized), scientists will transfer it into a surrogate mother to develop into a new animal.
Any animal created using this technique is not actually an identical clone of the donor animal – only the clone's nuclear DNA is the same as the donor. A small portion of the clone's genetic information comes from the egg cell's mitochondria, small structures that help make energy the cell.
What have we cloned so far?
In 1952, researchers cloned the first animal, a tadpole, and a decade later scientists cloned the first fish, an Asian carp. But it wasn't until 1996 that scientists cloned the first mammal from an adult somatic cell – the now world-famous Dolly the Sheep.
Since Dolly, scientists have cloned a growing number of mammals, including cows, pigs, cats, dogs and rhesus monkeys. In 2009, researchers even cloned a newly extinct animal, the Pyrenean ibex, though the cloned mammal died a mere seven minutes after birth.
What are the challenges to cloning?
There are a couple of challenges to reproductive cloning. First, somatic cell nuclear transfer has a high rate of failure – only about one or two out of 100 experiments result in a viable clone. With such a low success rate, cloning an animal – and especially mammals, which tend to have long gestation periods – can become an expensive endeavor.
Cloned animals also experience many health complications, such as abnormally large organs, and so they often die early. For example, scientists euthanized Dolly when she was six years old (half her expected lifetime) because she suffered from progressive lung disease and severe arthritis.
Is cloning humans legal in the United States?
There are no laws against cloning animals in the U.S. and there are no federal laws that ban human cloning completely. However, 13 states, including California, Iowa and Massachusetts, have state laws in place that ban reproductive cloning of humans.
Legal issues aside, some major organizations advise against human reproductive cloning on ethical grounds. Because of the low success rate for reproductive cloning and the likely health complications of cloned individuals, physicians from the American Medical Association and scientists with the American Association for the Advancement of Science publicly advised against human reproductive cloning. Additionally, religious groups raise other ethical concerns, such as the idea that reproductive cloning is "playing God." [ Report: Ban Cloning or Prepare for Consequences ]
Is cloning humans even possible?
Human cloning is not yet possible, but cloning technology is taking small steps in that direction. Much cloning research is actually focused on creating embryonic stem cells from the cloned embryo, rather than growing cloned humans (this field is called therapeutic cloning and is less controversial than reproductive cloning).
Recently, scientists at the New York Stem Cell Foundation Laboratory were able to create a developing cloned embryo, from which they were able to derive a self-reproducing line of embryonic stem cells. However, they did so without first removing the egg cell's, so the embryo was actually abnormal and had an additional set of chromosomes.