To have a healthy child it may no longer be sufficient to havejust an egg and sperm. In families in which they run, from generation to generation, disabling diseases such as muscular dystrophy or cerebral ataxia, the approach could be to undergo a new procedure for eliminating defective heredity in the laboratory.

Scientists at Newcastle University in the United Kingdom have shown that it is possible to create viable human embryos from the genetic material of two women and one man. The proof of concept has been published in the latest issue of the journal Nature. " If law changes, the new procedure could be available in three years in assisted reproduction clinics.

The technique is designed to prevent the transmission of mitochondrial diseases, a group of 150 diseases, infrequent, but devastating. Cause dementia, blindness, damage to the nervous system and vital organs like the heart and kidneys. Maternally transmitted through the DNA in mitochondria is outside the nucleus of the egg.

These structures are in all body cells, except in the blood. Mitochondria are responsible for producing the energy needed to live. A unique feature of mitochondria is that they have their own DNA from the mother.

To prevent the transmission of this DNA that can carry the disease, the technique takes a "mitochondria transplant" to an embrión.After the fertilization in vitro, they then extract sperm from the father and the mother's egg, containing DNA from the parents and leave behind the defective mitochondria. The nuclei were then implanted into the egg of a healthy woman who has been stripped of the nucleus and retains its mitochondria.

"What we do is like changing the battery of a computer. With the energy input working properly and the hard disk information is not changed, "says Doug Turnbull, head of research.

Mitochondria do not carry genetic information that defines the characteristics of a person. So the babies born by this procedure will resemble their parents 'real'. In his conception there were genetic elements from three people, but only the nuclear DNA of their parents which will influence their physical appearance and other characteristics.

With this procedure, we have created 80 viable embryos are not implanted in any woman. They remained alive in the laboratory for eight days until they reached the blastocyst stage. They were then destroyed, as a mark of British law.

The technique continues to be controversial because it involves the manipulation of the embryo and contains genes from three parents: the parents plus a small surplus of the mitochondrial DNA donor.