The Facts and Fiction of Cloning
Understanding the real science behind the headlines and the hubbub.
What Is Cloning? continued...
In nuclear transfer, DNA from an unfertilized egg is removed
and replaced with DNA from an adult body cell -- a skin cell, for example. When
the process works, the manipulated cell -- coaxed by the newly-implanted
genetic material -- begins to divide and eventually becomes a genetic replica
of the adult-cell donor. The process produces a new individual whose identical
twin is not a minute or two older, but already grown up.
Now, researchers in South Korea and the University of Michigan have cloned a
human embryo. This is not cloning to make a genetically matched baby, but
cloning for research purposes -- also called therapeutic cloning or research
This new development means that therapeutic cloning -- the ability to create
human clones for research purposes -- is no longer a theory, but a reality. And
it's sure to reignite the controversy of whether to ban all cloning or to allow
some cloning for therapeutic purposes.
Therapeutic cloning is not new. Scientists have used the technology to cure
a variety of diseases in mice. Scientists have also studied the potential uses
of human stem cells culled from embryos leftover in fertility clinics.
Embryo Successfully Cloned
Previous attempts to clone human embryos to obtain stem cells genetically
identical to the patient are believed to have failed despite reports to the
contrary -- until now.
In this new study, researchers collected 242 eggs donated by 16 South Korean
volunteers. Each woman also donated some cells from her ovary.
The scientists then used a technique called somatic nuclear transfer to
remove the genetic material -- which contains the nucleus of each egg -- and
replace it with the nucleus from the donor's ovarian cell.
Then, using chemicals to trigger cell division, the researchers were able to
create 30 blastocysts -- early-stage embryos that contain about 100 cells --
that were a genetic copy of the donor cells.
Next, the researchers harvested a single colony of stem cells that have the
potential to grow into any tissue in the body. Because they are the genetic
match to the donor, they aren't likely to be rejected by the patient's immune
"Our approach opens the door for the use of these specially developed
cells in transplantation medicine," says Woo Suk Hwang, a scientist who led
the research in South Korea.