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Scientists Produce Monkeys With DNA From Two Mothers

For their experiments, Mitalipov and his colleagues extracted DNA from the nucleus of monkey eggs; the nucleus contains the genes for most of a creature's traits. The researchers then transplanted that DNA into eggs from other females that had healthy mitochondrial DNA but from which the nuclear DNA had been removed.

They then fertilized the eggs in the laboratory and transferred 15 of the resulting embryos into the wombs of nine females. Two twins were born -- named Mito and Tracker -- along with two other offspring, Spindler and Spindy. So far, all the offspring appear to be healthy.

Several experts said the work should be tried in people only after much more research has been done to test its safety.

"The number one concern I would have is safety," said Mark Rothstein, a bioethicist at the University of Louisville. "There's always a concern that a facility might jump the gun and try to put it into use before safety has been established."

Even if further animal studies show that the approach is safe, attempts in humans might still lead to defective embryos, others noted.

"When it is attempted in humans, some abnormal embryos are bound to result. If they are discarded, this will raise major ethical concerns for those who view human embryos as nascent human beings, and by some who do not," said Cynthia B. Cohen, a Georgetown University bioethicist. "Many in our society are reluctant to see abnormal embryos created and then discarded."

If it works, said Lori B. Andrews, who studies ethical and legal issues raised by new reproductive technologies at the Chicago-Kent College of Law, women who donated the mitochondrial DNA could seek visitation rights.

"If the mitochondria donor (who is probably a young woman) is later infertile, she might seek visitation to the child," Andrews wrote in an e-mail. "After all, people didn't think surrogate mothers, who are not the nucleic DNA donors, would want access to the couples' genetic child, but some have gone to the courts for such access."

Others worried about opening the door to other genetic manipulation. "Unfortunately, we're likely to hear some people saying, 'Okay, we've done this, so why can't we alter the DNA in the nucleus to, say, prevent a predisposition to breast cancer? And if you do it for breast cancer, why can't we do it to weed out a predisposition to baldness?' " said Marcy Darnovsky of the Center for Genetics and Society.

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