Many serious genetic conditions can now be identified in embryos via a technique called pre-implantation genetic diagnosis (PGD). In addition to ensuring that affected embryos never see the light of day, this technique can identify embryos which would be carriers for a genetic condition, giving us the potential to completely eradicate a genetic condition from a population.
Many fertility clinics are now offering PGD alongside existing treatments. The process is fairly straightforward: it involves removing a single cell from an embryo and sequencing its genome. The genome is compared to a database of genetic conditions, and if any associated genetic abnormalities are identified in the embryo, it is discarded and a different, healthy embryo is implanted into the mother’s uterus.
PGD would commonly be used for couples who know that one or both of them carry a genetic condition, and PGD can ensure that the offspring are completely healthy and carry no trace of the condition. This benefits the whole population because it completely stops the genetic condition in its tracks and means that it can’t be passed on to future generations. This is nicely shown in the genetic pedigrees below, where the shapes filled in black represent individuals affected by a recessive genetic condition and the shapes filled in white represent healthy individuals. The pedigree on the left shows the normal inheritance pattern for a recessive genetic condition; and the pedigree on the right shows the inheritance pattern if couples 1-2 and 3-4 went through PGD.
There are hundreds of genetic conditions that can be identified via PGD: from achondroplasia (dwarfism) to XMEN syndrome. Some cancers, such as breast cancer have genetic predispositions, so PGD can help prevent the likelihood of cancer even before a person is born.
PGD evidently has many benefits, but it also rings a few alarm bells. PGD is primarily being used to screen for genetic conditions, but it can also be used to screen for a range of other characteristics, including eye colour and height. A previous article that I wrote outlines how some fertility clinics in the USA are offering eye colour selection to patients, and how this is potentially the start of a ‘designer babies’ movement.
Another problem with PGD is deciding which conditions are serious enough to select against. In the UK there is an authority on fertilisation and embryology. They have compiled a list of conditions which they deem acceptable to select against via PGD. The USA has no regulation regarding PGD, so parents could start selecting against trivial conditions that would have had little to no impact on their offspring’s quality of life.
This would eventually lead to a society in which everyone is completely devoid of any and all genetic conditions. Our imperfections build character and shape who we are; the struggles we endure help us to appreciate our lives more. It is unclear whether or not we would be happier if we were completely healthy.
A good example is a man called Brandon Colby. Brandon Colby suffers from an incurable genetic condition which causes him to ‘break out in painful blisters when exposed to heat and friction’ (see: Unnatural selection: Is evolving reproductive technology ushering in a new age of eugenics?). The condition effectively shaped his life, motivating him to get a medical degree and a business degree, start up a company and author a book. Without the condition, who knows what would have become of Brandon Colby? We can almost be certain that he wouldn’t have achieved the same level of satisfaction from his life.
While we consider the ethical ramifications of PGD, stronger regulation is needed to ensure that it is not used in a way we might eventually regret.