In vitro fertilisation: ethical problems of mitochondrial DNA and
three biological parents
Arttu Mäntylä, Bioethics course 2013
Mitochondria are essential for the cell energy production through the citric acid cycle. In order for
the cycle to work in a best way possible, the mitochondria are equiped with their own DNA that
primarily codes for proteins vital to the energy production and oxidative metabolism of the cells.
Mitochondrial DNA has several differences to nuclear DNA. Unlike the ”regular” nuclear DNA,
mitochondrial DNA in circular like most bacterial DNA and unlike nuclear DNA, mitochondrial
DNA is more prone to possible mutations. Mitochondrial DNA is also passed down from mother to
the child since the female egg provides most of the fetuses mitochondria and the male sperm's
mitochondria act in a minor role in the fertilisation process.
Due to the nature of mitochondrial DNA, genetic disorders typically pass down from the mother.
Mitochondrial diseases are characterized by changes in the cell energy production that often leads to
various manifestations, most of them related to growth and metabolism. In addition the disorders
are almost always lethal and cause the patient to die at a relatively young age.
Today women suffering from mitochondrial mutations have a choice if they wish to give birth to a
healthy child: in vitro fertilisation (IVF). In this case the nucleus of the women's egg would be
removed to a healthy womans enucleated egg. The formed egg would have nuclear DNA from the
intended mother and mitochondrial DNA from the female egg donor and would then be fertilized by
a sperm of the future father, thus resulting in three-party parenthood and hence the method is often
called three-parent in vitro fertilisation.
The transfer of the nucleus to an egg with healthy mitochondria also posses a possible risk. We don't
know if we've accidentally damaged the previously healthy mitochondria in the transfer. If the
mitochondrial DNA is damaged in the process of injecting the nucleus, the born child (a girl), would
transfer the possibly defective mitochondria to her offspring. However so far no such phenomena
have been described in the cases of in vitro fertilisation with nucleus transfer.
A child with three genetic contributors also raises many legal concerns that haven't been discussed
yet in most countries. In biological sense the child born has three parents. So should we determine
the parents trough the amount of DNA they've contributed to the developing fetus? Or should we
apply an alternative definition to biological parenthood? Currently Great Britain has approved the
use of three-parent in vitro fertilisation. In Finland the issues of three party IVF and the issue