It seems to have happened very quickly: it was only in 2012 that the public consultation process about allowing mitochondrial donation to be used on humans was underway; and now - if you'll allow the pun - the first child to have benefitted from them could be conceivable in the next few months. But this does depend on Parliament allowing an alteration to the terms of the Human Fertilisation and Embryology Act.
Currently, only 'permitted' embryos can be implanted in a woman; and a 'permitted' embryo is one derived from gametes that have not been genetically altered, and which itself has not been genetically altered. The proposed change in the law would widen the range of procedures that could be licensed by the Human Fertilisation and Embryology Authority (HFEA) to include mitochondrial donation. To all intents and purposes, it would allow for some genetic engineering of humans to allow some hitherto forbidden embryos to be implanted.
And there is good reason to make the change. Mitochondrial donation offers the chance to avoid a number of chronic health problems with high mortality and morbidity. It seems reasonable to say that, if we can avoid unnecessary suffering, this is an admirable thing; and mitochondrial donation does offer a way to avoid it. Whether it amounts to a duty is a slightly different question - and I'll come back to that in a moment. First, though, the arguments against. I think that they come in five basic varieties, but none is compelling.
The first is based on a concern about novelty. This is a very new procedure: there is no guarantee of its safety. Given that we're talking about human lives, this ought to give us pause, the argument goes. And, to be fair, it's hard to deny that it should - and safety is, of course, one of the things that the HFEA would have to have considered when licensing procedures (which is why even legalisation won't necessarily mean that mitochondrial donation is in use straightaway, if ever).
Having said that, any reproduction is a risky business, so there's nothing unique about mitochondrial donation on that front. Moreover, asking whether a technology is risky isn't the right question: we can assume that it is. The correct question is whether the risk is worth taking. If there is a chance that your child will inherit a distressing illness anyway, it might very well be. Besides: any treatment is experimental the first time it's used. 'We don't know what effect it'll have on humans' is an argument against any innovation whatsoever, which I take to be absurd. There are times when taking a risk is permissible, and times when it might even be desirable — and legalisation would make it easier to take what might be an desirable risk.
The second is that this technology puts us onto a slippery slope towards designer children. But this slope may not be so slippery after all. Even if these are in some sense 'designer' children, admitting that this instance of design is permissible doesn't imply that all design is permissible. We can worry about other alterations if and when they become possible. We could even try to bite the bullet entirely: the argument presupposes that designer children would be unequivocally a terrible thing. That might not be the case: for proponents of mitochondria donation, using this technology is paradigmatically a good thing, and they'll happily admit that they're designing children. 'Designer baby' is not a phrase that will faze them.
Third, there's a worry that this technology will distract from meeting the needs of people with mitochondrial illness, and possibly indicates a lack of respect for them as well. While it would certainly be a mistake to divert all our attention to the new technology though, it's not clear why anyone would think that that was a looming possibility anyway. On top of that, looking at ways to prevent illness in future no more need harm the interests of those who manifest it now or manifest it in future than looking at ways to make driving safer would make us less disposed to give due care to those in road accidents.
Fourth, there's a worry that we're changing human nature in some way: after all, this is a radical departure from normal parenthood, and will be passed down the generations. But, we might wonder, so what? If it's a change for the better, why not embrace it? In any case: the 'new' mitochondrial DNA (mtDNA) would be from humans, and amounts to a very small part of a person's genome; and, of course, any change will not make it past any sons anyway, since mtDNA is matrilineal. So any change in human nature is, in the grand scheme of things, small, and will likely be diluted out in a very few generations.
Finally, there's a concern for mothers who are at risk of passing on mitochondrial illnesses: might the procedure mean that there's a tacit pressure on them to reproduce in a way that they would prefer not to? This is a significant concern, I think — but it's not a concern about legalisation, since it's possible for something to be legal and available without generating pressure of any sort. Whether mothers-to-be have a duty to use the technology is a question for another time; but it's not implied by legalisation.
Does this mean that Parliament ought to make the change? Though it has a moral reason to, and little reason not to, it's not clear that this amounts to an obligation. Suppose Parliament were not to allow the procedure: would anyone actually be made any worse off? I don't think they would. This is not because of any version of the non-identity problem - I'm satisfied that mtDNA is such a small part of the cell that it isn't really identity-affecting.
No: my reasoning is based on the claim that it's hard to see that anyone would be wronged by not having had the procedure. For sure, someone born with mitochondrial illness might be worse off than they otherwise could have been - but that applies to all of us anyway. The point would stand, though, that we do not generally think that people are wronged by not being as well off as they counterfactually might have been; and since people with mitochondrial disease do have lives worth living, I don't think that they'd be able to claim to have been wronged by not having had the procedure. And that does deflate the idea that Parliament must alter the legislation.
Further, an obligation would ride on the higher-order claim that individuals have a right to offspring from their own gametes, and offspring of a particular sort. Neither of those claims is a given. A woman concerned about passing on a mitochondrial illness could adopt and still be a mother in the moral sense. If not passing on mitochondrial diseases is that big a concern for her - noting that it might not be - there are other ways to avoid doing so. Again, that takes away some of the urgency.
None of which is to deny that it would be good for the law to change. It would. If Parliament passes on the opportunity to legalise the procedure this time around, it might well have missed the chance to do something good. But it's not clear that it would thereby have done anything wrong. Being good is not the same as being obligatory.