A healthy baby boy was born utilizing a new "3 parent" technique, which combines DNA from 3 people. The technique is controversial and is, in fact, banned in the U.S. This did not stop a US-based team to perform the procedure in Mexico for a Jordanian couple in what is being called a breakthrough for fertility medicine.

The mother of the boy carries genes for the fatal Leigh Syndrome, which affects a developing child's nervous system. The syndrome affects a  quarter of her mitochondria, which is responsible for providing energy to cells.  The couple already lost two children to the genetic abnormality, one at age 6 and one at only 8 months old. 

To overcome the mutations in the mother's mitochondria, the DNA from her egg was placed in a healthy egg from a donor, which first had its nuclear DNA removed. Then this resulting egg was fertilized with the father's sperm.

The procedure has been controversial because it utilizes genetic material from a third person in addition to the couple. Critics see such research as going down the slippery slope of genetic engineering while scientists hail it as groundbreaking. 

“This is huge,” told Dr. Richard J. Paulson, president-elect of the American Society for Reproductive Medicine, to the New York Times.

Scientists hope that the success in this case can start changing attitudes towards procedures such mitochondrial transfers which they believe can help people. They point out that it's not really appropriate to call this a "3 parent" procedure.

As Dr. Paulson explained: “Mitochondria do not define who you are.” This is because genetic material for how a person looks and other characteristics are carried in the nuclear DNA, which is stripped from the donor's eggs in this technique.

The team performing the procedure was led by Dr. John Zhang, medical director of the New Hope Fertility Center in New York. His previous attempt to carry out the procedure in China in 2013 was unsuccessful.

Here's a helpful video from the New Scientist which summarizes the technique: