All opinions here are my own, I respect that other’s may have differing views.
As this is a genetics blog I thought I would write about MP’s voting overwhelmingly in favour of what the media have named three-person babies, this was despite opposition from some in the Church. While the Church, among other groups, has branded the procedure unethical I personally believe the opportunity to offer families a way to cure diseases caused by mitochondrial mutations is a wonderful thing for science to be able to do. I thought I would try to clarify some of the information around this news story.
Your mitochondria are the energy factories of yours cells therefore mutations in these genes can have severe consequences. As mitochondria are only passed to you by your mother (they’re found within the egg) mutations within them cannot be masked by a second functional copy as is often the case with genetic diseases passed on chromosomes. Many, although not all, genetic diseases are recessive, this means as along as you have a non-mutated copy of the gene from one parent you won’t express the disease. For mitochondrial mutations this is not the case, if the mother has a mitochondrial mutation it will be passed along and expressed.
Any babies born from this technology are not three parent babies, and this is not a stepping stone to “designer babies”. There is little difference between this and egg donation which uses donated eggs in IVF when a woman’s own eggs are unsuitable. In a similar way the eggs used in these procedures are donated. Those offered this procedure would just like to have children without any specific diseases caused by mutations in the genes of their mitochondria, not an unreasonable ask in my opinion, they aren’t aiming for babies where they can select “desirable” traits. Your mitochondria contain 37 genes, to put this in context the bacterial species I work on has ~2000 genes and you as a human have many more, so using donated mitochondria means that very little of the DNA comes from this third person – the donor. These mitochondrial genes are not the genes that make you who you are, they are genes that keep your cells ticking over.
There are two different methods that can be used for this procedure and they’re explained by this image from Nature News:
Pronuclear transfer is the technique that has been approved for use in the UK but Maternal Spindle transfer has been used by researchers in America to breed macaques, this has been done successfully and several of the macaques have reached the age of five and still appear to be healthy. Hopefully this can eleviate some of the concerns about potential incompatibilities of donated mitochondria with the parental DNA.
While we can’t rule out potential problems, this is the same for many advances in medicine. We don’t truely know if a drug will work to treat a disease until we try it, and the same is true here. However wasting this opportunity as we fear the possible outcomes would be a waste of scientific innovation and the potential to help many families who may have already been through significant suffering as a result of mitochondrial diseases. The law still needs to be passed by the House of Lords but this is unlikely to be a problem, paving the way for the UK to be the first country in the world to allow the creation of babies with DNA from three people (even if one of the contributions is tiny!).