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Mitochondrial disease. The condition varies wildly from patient to patient, striking at any age and with any number of symptoms, but all have one thing in common: the damage it inflicts on body and brain gets worse with age. There is no cure.
Though obscure outside specialist hospital units, mitochondrial disease will soon be the subject of a national debate and a matter for parliament. In a laboratory at Newcastle University, scientists are working on ways to prevent the disease by pushing medical genetics to the limit. But there is no guarantee that patients will ever benefit. Even if the techniques work safely, to offer them now would invite a jail sentence.
Because mitochondria provide energy for our cells, any genetic defect they pick up can make those cells run badly or break down completely. The worst affected parts of the body tend to be those that burn the most energy: the heart, brain and muscles. In practice, children who are diagnosed early in life often develop catastrophic multiple organ failure.
When sperm and egg meet, only the mitochondria from the mother's egg make it into the embryo and future child. But in women who carry the disease, one egg can be very different from another. In some eggs, 90% of the mitochondria might be defective; in others, only 10%. Whether or not the child will have disease depends on the biological lottery of which egg is fertilised.
People who inherit low levels of mitochondrial DNA (mtDNA) defects might have no health problems at all. But scientists are increasingly spotting the hand of mtDNA mutations in familiar conditions that are common in old age. In keeping with other mitochondrial diseases, they vary enormously, from diabetes, failing eyesight and deafness to Parkinson's disease and even obesity.
In Newcastle, Turnbull is working on ways to eliminate the risk of disease by replacing the mother's faulty mitochondria wholesale with those from a healthy donor. The use of this extra genetic material has led to headlines about "three-parent babies", a label Turnbull and many others in the field frown on. "It's very misleading because it assumes you're getting character from these genes. The makeup of our mitochondria has nothing to do with our characteristics. What makes you you and me me is not our mitochondria," he says.
One method Turnbull is testing is called maternal spindle transfer (MST). For this, doctors use standard IVF procedures to collect eggs from the mother. They then pluck the nucleus from one of the eggs and drop it into a healthy donor egg that has had its own nucleus removed. The new egg has all the mother's chromosomes, but the donor's healthy mitochondria, apart from a tiny portion of faulty ones that inevitably carry over with the mother's nucleus. The egg is then fertilised with the father's sperm, and the embryo implanted as a standard IVF procedure.
A second technique, called pronuclear transfer (PNT), is similar, except that both eggs are fertilised with the father's sperm first. Before the eggs have time to divide into early-stage embryos, the parents' chromosomes are removed from the mother's fertilised egg and dropped into the donor's.
One of the major objections to genetically modifying an embryo is that it might infringe the child's right to what bioethicists call an "open future". The concern is reasonable if a modification gives the child a certain hair or eye colour, for example, because the child may feel that they have been tailored to suit their parents' expectations. But preventing a child from inheriting a nasty disease gives them a more open future, not less, says Guido de Wert, professor of biomedical ethics at Maastricht University. Another issue that deserves attention is the impact on future generations, because biological faults introduced by the technique could be handed down from one generation to the next.
So...whats the issue here? Scientists have found a way to prevent people from suffering from a terrible disease? Why are people finding that to be unethical?
And the term which has been used for this, "Three-parent babies" show just how ignorant towards this stuff people are. With the first technique, all genetic information from the donor's egg has been removed, so there is nothing like a "third parent".
[Edited on 12.29.2012 4:00 AM PST]