Britain has become the first country in the world to allow the creation of human embryos from the DNA of three people, a technique intended to help mothers avoid passing on genetically degenerative diseases to their babies.
Members of parliament's House of Lords voted Tuesday to approve the controversial type of in-vitro fertilization that could prevent mothers from passing inherited health problems such as serious heart and brain disorders or muscular dystrophy. But critics see it as a step toward creation of so-called designer babies.
The House of Commons approved the move earlier this month.
Worldwide, about one in 6,500 children is affected by incurable mitochondrial diseases that could be limited by the genetic modifications.
The proposal is supported by key British medical authorities. They see the possibility of virtually eliminating the chance that women who are carriers of defective mitochondria, the energy-producing structures outside a cell's nucleus, could pass them on to their children.
Sally Davies, Britain's chief medical officer, said women should be given "the opportunity to have children without passing on devastating genetic disorders."
The proposal has drawn strong opposition from some medical ethicists, including David King of Britain's secular Human Genetics Alert. He said approval of the law would lead to a "eugenic designer-baby future."
The Roman Catholic Church, which is opposed to any artificial reproductive techniques, opposes the British proposal, as does the Church of England, which said last week there has not been enough scientific study of the medical techniques involved.
Medical personnel in Britain now will be allowed to remove the nucleus DNA from the egg of a prospective mother and insert it into a donor egg from which the nucleus DNA has been removed. The resulting embryo then has the nucleus DNA from its parents, but the normal mitochondrial DNA from its donor. Scientists say the resulting embryo's genes have less than 1 percent of the DNA from the donor egg.
No mitochondria replacement treatments have been approved anywhere. The U.S. Food and Drug Administration last year discussed the techniques under consideration in Britain, but decided it was too soon to use them in humans. Monkeys have been produced using one of the laboratory techniques.
One U.S. opponent of the procedure is Wesley Smith, a senior fellow at the Discovery Institute's Center on Human Exceptionalism. He told VOA it would further "the commodification of reproduction." He said prospective parents some day will have the chance to have "the kind of baby they want."
He said that while he understands the suffering of mothers with a genetic disorder, "the welfare of future children and the moral health of society must count for more."