Human Embryos Created with Three “Genetic Parents”

Biologists in Oregon are announcing the creation of human embryos with three “genetic parents.” Here’s the basic idea: human cells contain genetic material in the cell’s nucleus, which is a combination of the mother’s and the father’s DNA. Cells also contain structures called mitochondria, which, among other things, help the cell produce energy in usable forms. The important point is that the mitochondria contain their own genetic material, apart from that in the nucleus, and are derived exclusively from the mother. When an egg cell is fertilized, its nucleus now contains genetic material from both parents. The mitochondria, however, are already present in the egg cell from the start, and all subsequent mitochondria in the body are derived from these maternal, egg-cell mitochondria.

Some diseases are associated with damaged mitochondria, so the biologists in Oregon have developed a procedure by which the nucleus is removed from an egg cell from a woman with a mitochondrial disease,and then placed into a second egg cell, taken from another woman with healthy mitochondria, from which the nucleus has been previously removed. This produces a new composite egg cell with a nucleus containing the genetic material of one woman, and mitochondria (plus all the other cellular components) from a second woman. When this egg cell is then fertilized in vitro, it contains genes from three sources: the nuclear genes from the first woman and the father, and the mitochondrial genes plus maternal cellular components from the second woman. The idea is that women who would otherwise pass on mitochondrial diseases to offspring will now have a way to “produce” offspring with their own nuclear DNA, but without the defective mitochondrial genes.

For the Nature story on this development, see here. For Rebecca Taylor’s (Mary Meets Dolly) commentary, see here.

Three years ago, when this same team of biologists announced their first trial of this technique in rhesus monkeys (rather than in humans, as in the current announcement), bioethicist Fr. Tad Pacholczyk offered some commentary on the ethical issues surrounding this technique:

“To put it simply, our children have the right to be procreated, not produced. They have the right to come into the world in the personal, love-giving marital embrace of their parents, not in the cold and impersonal glass world of a test tube or petri dish. They have the right to be uniquely, exclusively and directly related to the mother and father who bring them into the world. IVF ignores all these rights of the child.

The second objection to mitochondrial swapping in humans is that it would introduce a rupture into parenthood by creating children who inherit genetic material from three parents. While the mother and father would contribute the majority of their child’s DNA from their own egg and sperm, a small amount would come from a second woman donating healthy mitochondria from one of her eggs. In other words, the procedure dilutes parenthood by introducing another parent, another woman, into the procreation of the child.

In the mitochondrial swapping scheme, it is significant that not just the mitochondria are “swapped” but actually all the other structures of the cell come from the second woman’s egg as well (except for the nucleus and its chromosomes). In other words, one woman provides the DNA from her own chromosomes, while another woman provides everything else: all the other subcellular machinery of the egg, including the mitochondria. In summary, then, we are not actually “repairing” a defective egg, but constructing a new, alternative and clearly different egg out of the contributions from two separate women. The final egg produced really belongs to neither woman, so that the technological manipulations introduce a fissure between any child conceived from the engineered egg and both “mothers.” The child becomes “distanced” or “orphaned” from both women involved in the process.”

(Arlington Catholic Herald)

Fr. Pacholczyk’s second objection is, I think, especially easy to overlook in our modern biological mindset of “genetic reductionism”. (I think that some pro-lifers even make this error when they insist on the “uniqueness of the DNA” as determinative of the humanity of the unborn—that DNA is, I think, diagnostic, but not determinative.) The child that is produced from this technique, while of course no less human and dignified than any other, is really the product of the biological contributions of three parents. The hubris of deliberately subjecting a child to this confused situation in order to fulfill our desire for complete control over nature is at the heart of the moral objection to these scenarios, however well-intentioned they may be.

Comments are closed.