Britain has become the first country to pass a law allowing "three-person babies" to be created from DNA from three people in a technique that can prevent genetic diseases from being passed down from mother to child.
The new measure approving the modified form of in vitro fertilization passed its last legislative hurdle when the House of Lords of the British Parliament approved it.
Developed be the University of Newcastle, the "three parent" technique is an attempt to avoid diseases caused by mutations in a mother's mitochondrial DNA being passed down to her children.
Mitochondrial diseases, thought to afflict as many as one in 5,000 people, can involve brain damage, blindness or heart failure in addition to other ailments.
The newly approved technique involves a modified version of in vitro fertilization in which the mutation is removed from the DNA of the mother, replaced with healthy mitochondria of a donor woman before being combined with the father's DNA
Babies born of this procedure would have 0.1 percent of their DNA from the donor woman.
The House of Commons approved the measure earlier this month, not without considerable debate.
"This is a bold step for parliament to take, but it is a considered and informed step," Public Health Minister Jane Ellison said during the Commons debate.
"And for the many families affected, this is light at the end of a very dark tunnel."
That was echoed by Lord Howe, saying the technique offered "real hope" to families.
"It would be cruel and perverse in my opinion, to deny them that opportunity for any longer than absolutely necessary," he said.
During the Commons' deliberations, other MPs had expressed concern because the donor DNA introduces a permanent genetic change that could affect succeeding generations.
"[This] will be passed down generations, the implications of this simply cannot be predicted," MP Fiona Bruce said.
"But one thing is for sure, once this alteration has taken place, as someone has said, once the gene is out of the bottle, once these procedures that we're asked to authorize today go ahead, there will be no going back for society," she said.
Although both the Catholic and Anglican churches had expressed opposition to the procedure, and some groups warned it could open the door to so-called designer babies, the votes in the Commons and in the House of Lords were greeted with approval by many in the scientific community.
"Britain is the first country in the world to permit this treatment, and it is a testament to the scientific expertise and well-respected regulatory regime that exists across the United Kingdom that Parliament has felt able to approve it," said Sally Cheshire, the chairwoman of the Human Fertilization and Embryology Authority.