Three-parent IVF has been the focus of discussion and debate in the media over the last several weeks. Greene’s Biology tutor, Catherine Offord, explains what three-parent IVF is, how it works, and the complex ethical issues that it raises. Catherine is a Biologist, specialising in animal behaviour. She gained her first degree in Biological Sciences at the University of Oxford (St. Hilda’s College). Having graduated, Catherine worked as a laboratory assistant and as the Greene’s Science Co-ordinator. She is now studying for a postgraduate degree at the University of Princeton, U.S.A.
Approximately 1 in 6,500 people is affected by a serious mitochondrial disease, but recent research at Newcastle University may offer a way for parents to avoid passing on such genetic defects to their children. Developing a method similar to that used to clone Dolly the sheep, the technique involves removing the nucleus of a fertilised egg cell and implanting it into a donor cell with healthy mitochondria.
To understand what types mitochondrial diseases can be adverted by three-parent IVF, we first have to understand the crucial role mitochondria play in a cell. Mitochondria are organelles which carry out aerobic respiration in the cell; they are essential to providing every cell with energy—without properly functioning mitochondria, many energy-requiring organs in the body such as the brain, heart and kidney are seriously affected.
Although most genes are contained in the nucleus of the cell, 37 functional genes are contained in DNA that is only present in the mitochondria. About 1 in 200 children is born with a mutation in this mitochondrial DNA, but usually this mutation has little or no effect. However, mutations in protein-coding genes may cause life-threatening conditions such as muscular fatigue and heart failure.
During fertilisation, mitochondria are contributed from the female egg but not the male sperm cell and are therefore only passed on to children from the mother. Any genetic defects in the maternal mitochondria could thus be transmitted from mother to child. To prevent this transmission, scientists at Newcastle have pioneered a method which removes the fertilised nucleus of the mother’s egg cell (containing the nuclear DNA of both the mother and the father) and implants it into an empty donor egg cell containing mitochondria with healthy mitochondrial DNA. This recombined egg cell is then implanted back into the mother and the baby is born normally. Speaking to the BBC, Professor Doug Turnbull summarised the procedure as like “changing the battery on a laptop”, that is, simply replacing the energy providers—the mitochondria. The method is called ‘three parent in vitro fertilisation’, or ‘three parent IVF’, because there are three sources of genetic material: the mother, the father and the donor of the egg cell containing healthy mitochondria.
This ‘three-parent IVF’ procedure has been referred to the Human Fertilisation and Embryology Authority where it will need to be approved before it can become licensed for use in IVF clinics. However, ethical concerns have been raised due to the unusual and some would say ‘unnatural’ parentage of the children born as a result of this method. Should we endorse a procedure that results in a child having, technically speaking, three parents?
The development of techniques which interfere with embryonic DNA confronts us with interesting questions about the role of science in society. Currently, the use of three-parent IVF has been proposed only for the avoidance of serious disease, but even in the name of disease prevention, many have described this technique and others like it as attempts to ‘play God’. So-called ‘designer babies’—children born who have had genetic traits such as eye colour selected by their parents during IVF—may still be a long way off, but this latest milestone in our modification of the genetic code reminds us of the important question of whether we should be using such scientific techniques just because we can.
The Newcastle University Biology website: http://www.ncl.ac.uk/biology/