Some women are carriers of a genetic disease because of defective mitochondria. Replace hers with healthy mitochondria donated by a another woman. Result: a healthy child. Problem solved. What’s to worry about? Plenty.

Some women are carriers of a genetic disease because of defective mitochondria. Replace hers with healthy mitochondria donated by a another woman. Result: a healthy child. Problem solved. What’s to worry about?

But in a ferocious blast in the on-line journal Public Discourse, University of Utah stem cell scientist Maureen Condic contends that there are significant ethical and medical problems with so-called “three-parent embryos”

Supporters of the technique frame it as if it were as simple as popping some extra RAM into a laptop to make it run faster. But Dr Condic looks at it differently. She analyses the three methods of “therapy” and concludes that they are all “macabre form[s] of eugenic cloning, in which a human being with a medical condition is killed and his or her parts are used to create a new human being with an improved biological state.”

She also disputes the ethics of the “extra RAM” approach:

“The embryo produced by this procedure is not just the original child of the parents, moved to a new cytoplasmic ‘environment’. This would only be true if a human being were nothing more than his or her DNA, which is clearly not the case. While our unique DNA clearly determines many aspects of our individual characteristics, we are also greatly influenced by the specific, non-genetic composition of the egg that produced us.”

There are also serious concerns about the health of the resulting embryo.

“All three [methods of ‘mitochondrial transfer’] are highly likely to be unsafe for the resulting children, even the ones that are not deliberately destroyed and are not damaged by the procedure itself. Mitochondrial heteroplasmy, or the persistence of some mitochondria from both the mother and the donor egg, is a significant risk to any children produced by these techniques. In general, heteroplasmy is not a good thing, and in this case, it could also cause reappearance of the disease in the offspring of any woman produced by the “three-parent” approach, due to mitochondrial ‘founder effects’ in oogenesis. Even a few ‘bad’ mitochondria can become the dominant type in any one egg, causing the mitochondrial disease to recur in any child produced from that egg.”

Finally, the technique could create another serious inheritable problem:

“We know that in nature, mtDNA and nuclear DNA ‘co-evolve’ to work with each other in an efficient manner. In some species, incompatibility between the mitochondrial and nuclear genome significantly compromises the health of the individual. All of the proposed methods of ‘treating’ mitochondrial disease introduce a permanent and unnatural mismatch between the nuclear and the mitochondrial genome that will be inherited by all subsequent generations.”

Michael Cook
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Michael Cook

Michael Cook edits BioEdge, a bioethics newsletter, and MercatorNet, an on-line magazine whose focus is human dignity. He writes from Sydney, Australia.

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