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When a Massachusetts
biotech company recently declared that its researchers had cloned human embryos,
it conjured up scary images for many people: bad science-fiction movies,
Hitler's twisted ambitions, rows and rows of identical humans.
But, like most things in life, the truth is a lot more complicated, more
subtle.
The announcement drew a storm of criticism.
Ethicists, religious leaders and US President Bush denounced Advanced Cell
Technology for going too far. Scientists charged that the experiment was hyped
and called it a failure.
The news put a spotlight on the field
of cloning, from work with animals to researchers' efforts to use cloning to
create tissues for people suffering from debilitating and fatal
diseases.
At its most basic level, cloning means creating
copies, and in many ways, cloning has been around a long time. When someone cuts
a shoot off a green spider plant and re-pots it, that person is creating a
clone. Scientists clone or copy genetic material, or DNA, to match suspects to
crimes. By copying cells, researchers have been able to create and test drugs.
Scientists even use cloning techniques to create copies of the human gene for
insulin to help make insulin for people with diabetes.
"Cloning
per se is not bad. The ability to clone and make lots of copies of DNA
molecules and cells is part of the entire biological revolution and all sorts of
good stuff," sags Larry Goldstein, professor of cellular medicine at the
University of California, San Diego, School of Medicine.
Cloning
a whole animal or a human being, however, is a much more difficult proposition,
even without considering the moral implications. The basic method sounds
deceptively simple. Scientists allow an egg to mature in a culture dish.
They strip out the genetic material from this egg. Then they insert the
genetic material of a separate cell, an adult cell. Next, using a chemical
mixture or electrical stimulation, researchers trick the egg into thinking it
has been fertilised by sperm. This will activate the cell to start
dividing.
Essentially, scientists are trying to reprogramme the
egg to create a new organism. It's an excruciatingly difficult process.
During the past several years, scientists around the world have used this
method to clone animals. They've created about a half-dozen different species,
including the famous first sheep, Dolly, along with cows, mice, goats and pigs.
Experts say these cloned animals could offer a great deal, from herds that
produce more milk, to genetically modified animal organs that could be used for
transplantation in humans, and even to cattle that lack the gene that makes them
susceptible to mad cow disease.
But it has been a tough
process. For each species, scientists have had to work out subtle variations on
the basic cloning steps, including how to treat the donor cell and what type of
stimulation to use to spark the egg to start dividing. Still, fewer than 1% of
these cloned embryos produce live offspring.
Even those born
alive have abnormalities--some become obese very quickly, some suffer neonatal
respiratory failure. Those that die do so suddenly, and scientists can't figure
out why.
There is no consensus about what is going wrong in
these experiments or why, except that something must be awry in the genetic
reprogramming. But almost all scientists agree that aside from the moral debate,
cloning hasn't been perfected enough to try in humans.