Mitochondria disease is passed on from a mother's egg. Mitochondrial disorders cause serious health problems in children, and many of them die prematurely because of the inability to produce the energy for growth. There is no effective treatment for mitochondrial disease at the moment.
However, some research done on mice suggested that it may be possible to overcome this by using the eggs of healthy donors. Two eggs would be used to produce an egg with healthy mitochondria by taking the cell cytoplasm from a donor woman and combining it with the nucleus of an egg taken from a woman with mitochondrial disease who wants to have her own genetic child.
This technique is quite similar to cloning technique, the difference is that sperm will still be used for in-vitro fertilization.
The procedure was not allowed at first. The main reason was that the procedure prohibits alternation of the genetic structure of any cell while it forms part of an embryo. After placing an appeal, the procedure was reviewed again and approved stating its importance to finding a way to allow mothers with mitochondrial disease to have healthy children.