The major ethical difficulties entailed should not be forgotten, since in addition to those of human cloning, it would have those derived from the production of embryos, would have two mothers and one father.
The exchange of genetic material between oocytes and embryos offers a new reproductive option for the prevention of mitochondrial diseases. It has been found that mitochondrial dysfunction could be a cause of major diseases that can affect various organs. Tissues with high energy demands, such as the brain, heart, muscles and central nervous system, are severely weakened when there are mitochondrial abnormalities. Mitochondrial diseases can be due to mutations in mitochondrial DNA or in the nuclear genes involved in mitochondrial function.
There is currently no effective treatment for patients with mitochondrial diseases, so great emphasis is being put on preventing the transmission of these conditions.
One new possibility in this respect is cloning using nuclear transfer between oocytes, which essentially consists of extracting the nucleus of the oocyte from a woman who has abnormal mitochondria and transferring it to another oocyte of a healthy woman, in whom the nucleus has already been extracted. In this way, a new oocyte is obtained with the mitochondria from the oocyte of the healthy woman and the nucleus of the affected woman. This new oocyte can be fertilised with sperm from a healthy donor, so that a blastocyst would be obtained that was unaffected by the mitochondrial disease suffered by the patient (Fertil Steril 101; 31-35, 2014).
Although the technical application of this technique appears a long way away, because as we know, human cloning has yet to be achieved, it has been proposed from various research fields related with assisted procreation.
Moreover, the major ethical difficulties entailed in this technique should not be forgotten, since in addition to those of human cloning, it would have those derived from the production of embryos, which if viable (which is doubtful) would have two mothers and one father.
Summary: Nuclear transfer between oocytes enables a hybrid to be created from the oocyte of a woman with mitochondrial disease and another from a healthy one. The hybrid can then be fertilised, thus avoiding the possibility of transmitting mitochondrial diseases. This technique is still a hypothetical possibility for reproductive purposes, in addition to entailing major ethical problems.