British scientists revealed this week that they have been able to create a human embryo using DNA from three parents, a momentous medical progress that could help prevent severe hereditary diseases.

Researchers from Newcastle University, in northern England, revealed their breakthrough during the Medical Research Council Centre for Neuromuscular Diseases conference in London on February 1-2, Reuters reports.

The scientists were able to create test-tube embryos using DNA from one man and two women, in an attempt to prevent the transmission of diseases from women with faults in their mitochondrial DNA to their children.

Such defects in the female DNA can lead to some forms of epilepsy, diabetes, heart failure, mental retardation and other conditions. Mitochondria provide cells with most of the indispensable energy but faults in their genetic code can lead to incomplete processing of food and oxygen. This in turn can lead to the development of more than 40 different diseases, Reuters notes.

In order to allay fears of genetically modified babies, the scientists emphasized that they only sought to bypass the risks of defective mitochondria in a woman's egg. The process employed by the Newcastle team involved embryos created from one man and one woman with defective mitochondria; the embryo was then transplanted into an emptied egg from a second woman who had healthy mitochondria.

“We are not trying to alter genes, we're just trying to swap a small proportion of the bad ones for some good ones,” Patrick Chinnery, a professor of neurogenetics at Newcastle University, was quoted by The Associated Press as saying.

Chinnery and colleagues explained that these were only the preliminary phases of their research and that further testing was needed. The embryos created so far were destroyed within six days.

Should a fetus be allowed to develop, it would inherit nuclear DNA, or genes, from both parents but mitochondrial DNA from a third party.

BBC News notes that no treatment for mitochondrial diseases exists currently.