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January 13, 2000
Web posted at: 6:29 p.m. EST (2329 GMT)
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In this story:
How they did it
Why do scientists need identical monkeys?
Testing nature against nurture
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From staff and wire reports
BEAVERTON, Oregon (CNN) -- Oregon researchers say they have cloned
a monkey by splitting an early-stage embryo and implanting the
pieces into mother animals.
The technique, detailed in Friday's issue of the journal Science,
has so far produced only one living monkey, a bright-eyed rhesus
macaque female named Tetra, now 4 months old.
Professor Gerald Schatten, a researcher at the Oregon Health
Sciences University in Portland who led the research, said four
more animals are on the way.
"This is essentially the method of Brave New World,"
said Ronald M. Green, an ethicist at Dartmouth College. "This
opens the prospect of mass identical replication."
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Schatten said the team's goal was to
produce identical monkeys that could be used to perfect new therapies
for human disease.
How they did it
Tetra the monkey is different from Dolly
the sheep, which was produced by Scientists at Scotland's Roslin
Institute using a process called nuclear transfer -- taking the
nucleus out of an adult cell and using it to reprogram an unfertilized
egg.
Some scientists argue that animals like Dolly are not 100 percent
clones because they have genetic material both from the adult
cell they were taken from, and from the egg that is hollowed
out to make the clone. Tetra was produced by a technique called
"embryo splitting." Here's how it works:
* An egg from a mother and sperm from
a father are used to create a fertilized egg.
* After the embryo grows into eight
cells, researchers split it into four identical embryos, each
consisting of just two cells.
* The four embryos are then implanted
into surrogate mothers. Schatten said that in effect, a single
embryo becomes four embryos, all genetically identical.
In the case of their experiment, three
of the embryos didn't survive. The fourth, Tetra, was born 157
days later. Her name means "one of four." Tetra isn't
the first monkey to be cloned, but she is the first using the
embryo-splitting technique. More are on the way.
Schatten said that four mother monkeys are pregnant with cells
taken from two separate embryos. Three of the mothers were implanted
with two unrelated embryo splits and the fourth mother was impregnated
with a single embryo split. The babies are due in May.
"It is possible that we will have genetically identical
monkeys born to different mothers," he said.
Schatten says the "embryo splitting" process is similar
to what happens in nature when a mother has twins. "This
is just artificial twinning," he said. The method is commonly
used in animals such as cattle but had never before been used
to create a monkey.
The technique also has been used to create clones of human embryos
at least once. In 1993 Dr. Jerry Hall said he had cloned human
embryos by splitting them, although he said the clones were destroyed.
The cloning procedure began with an eight-celled embryo that
was split into four two-celled embryos
Why do scientists need identical monkeys?
Currently, most medical therapies are
first tested in mice, but monkeys are much closer to human biology
and would be more reliable in developing daring new techniques
such as gene therapy or growing new organs using stem cells,
Schatten said.
"It is a huge leap from a mouse to a patient," Schatten
said. "The monkeys could fill that scientific gap."
But Schatten said it's virtually unknown for identical twin rhesus
monkeys to be produced naturally. "What we're on the road
towards is making identical twins, identical triplets, and the
identical quads which could serve as the models for treating
the life-threatening diseases that still plague us today,"
he said.
"This is very exciting and very important," said Dr.
John Strandberg with the National Institutes of Health. "I
can't think of a single kind of monkey-based research that wouldn't
benefit from using identical animals."
Strandberg said identical animals are so valuable that researchers
often inbreed mice or rats to obtain nearly the same effect.
Testing nature against nurture
Cloned monkeys also would also facilitate
an important of test the old argument of whether nature or nurture
plays a bigger role in development of offspring. "We could
learn what the environmental effect is, separate from genetics,"
Schatten said. "There are theories that maternal environment
can result in an IQ drop of around 10 points."
There are theories that influences in pregnancy have consequences
very late in life, he said.
For example, the children and even grandchildren of malnourished
women may be prone to heart disease and diabetes.
"By taking say a set of triplets and putting them into three
different moms ... you could have one mom listen to Mozart, another
heavy metal and maybe NPR (U.S. National Public Radio) for a
third. And maybe you could have the very same baby born in the
very same mom but in a sequential pregnancy. These are answers
that we need today."
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Researchers clone monkey by splitting embryo