LONDON — In a landmark decision that some ethicists warned is a step down the path toward “designer babies,” Britain gave scientists approval Monday to conduct gene-editing experiments on human embryos.

The researchers won’t be creating babies – the modified embryos will be destroyed after seven days. Instead, they said, the goal is to better understand human development so as to improve fertility treatments and prevent miscarriages.

The decision by Britain’s Human Fertilisation and Embryology Authority marks the first time a country’s national regulator has approved the technique.

Permission isn’t explicitly required in many other countries, including the United States and China.

The United States does not allow the use of federal funds for embryo modification, but there is no outright ban on gene editing.

Gene editing involves deleting, repairing or replacing bits of DNA inside living cells in a biological cut-and-paste technique that scientists say could one day lead to treatments for conditions such as HIV or inherited disorders such as muscular dystrophy and sickle cell disease.

A team led by Kathy Niakan, an embryo and stem cell specialist at London’s new Francis Crick Institute, received the OK to use gene editing to analyze the first week of an embryo’s growth.

The research will “enhance our understanding of IVF (in vitro fertilization) success rates by looking at the very earliest stage of human development,” said Paul Nurse, director of the institute.

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