THURSDAY, Oct. 25, 2012 — If you thought juggling two parents was a lot to handle, try adding in a third!  Genetic manipulation of human eggs may be the key to curing potentially lethal and rare mitochondrial diseases in unborn babies, but the process involves a third-party egg donor, challenging conventional ideas of genetic inheritance and parenthood, according to a new study in Nature.

In the United States alone, 1 in 4,000 children are born with mitochondrial diseases, according to the United Mitochondrial Disease Foundation.

Mitochondria, commonly referred to as the power plants of cells, convert glucose to energy and reside in all cells within the body except red blood cells. Mitochondria house their own DNA, which is inherited by a child from the mother. Mitochondrial failure affects body parts that require high energy, like the brain and muscle. Frequently misdiagnosed, mitochondrial mutations can cause blindness, deafness, strokes, seizures, and cardiovascular problems. They have also been linked to multiple sclerosis and Parkinson's disease.

Scientists at the Oregon National Primate Research Center and Oregon Health and Science University, led by reproductive biologist Shoukhrat Mitalipov, PhD, have identified a possible process to prevent these diseases. In the research, the process worked like this: They removed chromosomes, which carry cell nuclei containing DNA, from human egg cells predisposed to genetic mutations. They then placed the chromosomes into healthy donated eggs and fertilized them through in vitro, thus creating human embryos.

Three years ago, the Oregon scientists had tested stem cell samples from macaque monkeys who had undergone this procedure and confirmed that they could effectively replace DNA in mitochondria. That experiment resulted in the births of four healthy baby monkeys; the technique also worked with donor eggs that had been frozen.

Half of the human eggs tested experienced incomplete splitting of cells and had remnants of the mutated maternal DNA, but 20 percent of the eggs produced viable embryos. “It looks like human oocytes are more sensitive” than those of the macaques, said Mitalipov in the Nature article.

Although there has not yet been a human pregnancy using this technique, Mitalipov expressed confident in his team's discovery. “You can expect the first healthy child to be born [using this method] within three years," he said in Nature.

“From my point of view, this has big implications in women who have some type of mitochondrial DNA mutation,” Carla Koehler, a mitochondrial biologist at UCLA, told NBC News.

Children conceived using this mitochondrial DNA process would not have the risk of developing the mutation found in the mother. But the process raises ethical issues because it combines the genetic material of a mother, a father, and an egg donor — thus spawning concern over what the Nature article called the creation of a "hybrid three-parent baby."

The new technique still has to undergo human trials and has not yet been approved by any federal agency.