The team of scientists in Newcastle aims to treat up to 25 patients per year, resolving problems related to mitochondria, the minuscule structures that produce energy inside cells.

"Mitochondria diseases can be devastating for families affected, and this is a momentous day for patients," said Doug Turnbull, director of the research at Newcastle University on Thursday.

Such disorders are passed down the maternal line and affect around one in 6,500 children worldwide. They can lead to serious conditions such as muscular dystrophy and organ failure.

To bypass the problem, scientists take the DNA of the future mother from her egg and put it in a donor egg, from which the original DNA has been removed. The donor egg contains healthy mitochondria, which are then passed on to the child. Ultimately, the child would have about one percent of DNA from the donor, with his two parents accounting for the remaining 99 percent.

Regulator still keeps watch

Last year, US-based doctors said that they successfully used the technique in Mexico, and that the first baby had been born. The researchers traveled to Mexico because the procedure had not been approved in the US.

Opponents of the treatment fear that it could lead to so-called "designer babies," allowing future parents to choose their children's genetic make-up. Its proponents, however, say it is a significant milestone to circumvent incurable diseases.

The UK parliament first opened the door for this procedure in 2015, and later voted to change the law and allow the treatments once they were ready for licensing.  The UK's Human Fertilisation and Embryology Authority (HFEA) decided to offer licenses for this treatment in December. The decision on Thursday marked the first time such a license has been granted. However, the scientists would still need to ask for approval in each individual case.

Allan Pacey, a fertility expert at Newcastle University, said that the decision was "a great day for science."

dj/jm (AP, Reuters)