The aim of the project is to shed light on "the genes human embryos need to develop successfully," the Francis Crick Institute says in a statement.
The research could improve embryo development after in vitro fertilization or advance treatment of infertility.
"The work carried out at the Crick will be for research purposes and will look into the first seven days of a fertilized egg's development (from a single cell to around 250 cells)," the institute says. The researchers will use donated, surplus embryos from IVF treatments.
"The decision permits [Crick team leader Kathy] Niakan to study the embryos for 14 days for research purposes only," The Guardian reports. "It does not permit them to be implanted into women."
This kind of research is possible because of a technique called CRISPR-Cas9, which was first demonstrated three years ago. It allows scientists to cut DNA with precision and replace it, making it much easier and cheaper to modify genes. This video from MIT's McGovern Institute for Brain Research shows how it works:
The machine has revolutionized genetic engineering but has also provoked ethical questions about what scientists should be allowed to do with it. NPR's Rob Stein has reported on the heated debate:
"Scientists believe the new techniques will produce many benefits, such as finding new ways to prevent and treat diseases, including AIDS, cancer and Alzheimer's.
"But the ability to edit DNA so easily is also raising many fears, especially about the prospect of changing human DNA from the very start. Scientists explored how altering sperm, eggs and embryos could yield important new insights into basic human biology and development, and help prevent and treat many inherited diseases, including Huntington's disease, cystic fibrosis and Tay-Sachs disease.
"But altering the so-called germline in this manner has long been considered off-limits. That's because such changes can be passed down to future generations. Mistakes could inadvertently introduce new diseases into the human gene pool."
And at the extreme end, Rob says "another fear is that taking this step would open the door to designer babies" — kids modified to be especially smart or attractive, for example.
Supporters of Monday's decision in the U.K. argue that it is "balancing the benefits to research and ethical considerations," the Guardian reports.
Sarah Norcross, director of Progress Educational Trust, told the newspaper that it represents "a victory for level-headed regulation over moral panic."