The creation of babies whose DNA has been altered to give them what parents perceive to be the best chances in life has received a cautious green light in a landmark report from a leading UK ethics body.
The Nuffield Council on Bioethics said that changing the DNA of a human embryo could be "morally permissible" if it was in the future child's interests and did not add to the kinds of inequalities that already divide society.
The report does not call for a change in UK law to permit genetically altered babies, but instead urges research into the safety and effectiveness of the approach, its societal impact, and a widespread debate of its implications.
"It is our view that genome editing is not morally unacceptable in itself," said Karen Yeung, chair of the Nuffield working group and professor of law, ethics and informatics at the University of Birmingham. "There is no reason to rule it out in principle."
But the report drew immediate criticism from some quarters, with one lobby group accusing the authors of opening the door to the unrestricted use of heritable genetic engineering, and an age of genetic haves and have-nots.
Recent advances in genetic technology have given scientists the tools to rewrite the DNA bound up in living cells, letter by letter. With the procedures in hand, scientists can in principle tweak the genetic code in sperm, eggs and embryos, and change dramatically how future children develop.
While laws in the UK and some other countries currently ban the creation of genetically altered babies, a handful of experiments around the world have shown that DNA editing could, in principle, prevent children from inheriting serious diseases caused by faulty genes.
The prospect of modifying genes in human embryos has long been controversial though. For a start, the procedure has yet to be proven safe. In a study published in Nature Biotechnology on Monday, British researchers found that the most popular tool for genome editing, Crispr-Cas9, caused more damage to DNA than previously thought. If the scientists are right, gene editing could disrupt healthy genes when it is meant only to fix faulty ones.
Another consideration is that any changes made to an embryo's DNA would affect all of its cells, including the sperm or eggs, meaning that genetic modifications would be passed down to all future generations. Also, in the vast majority of cases alternative procedures, such as preimplantation genetic testing, can be used to screen embryos for harmful DNA.