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Mitochondrial Replacement Slippery Slope?

The UK government's recent decision to move toward enabling human trials in which mitochondrial replacement from donor DNA would be used to treat mitochondrial disease in embryos has stirred up a predictable ethical debate. Does this step effectively green-light human germline modification, a step possibly towards even more profound human genetic engineering?

In a commentary in Nature, Marcy Darnovsky, executive director of the Center for Genetics and Society, says that mitochondrial replacement procedures do constitute germline modification, and that allowing these procedures to move ahead "would unilaterally cross a legal and ethical line" that has been drawn and observed by the international community.

She writes that the broad consensus is that genetic engineering tools may be used to treat an individual's medical condition, but that they should not be used to "modify gametes or early embryos and so manipulate the characteristics of future children."

Darnovsky says that such a treatment is not necessary in most cases, because women with mitochondrial diseases have alternatives, such as pre-implantation genetic diagnosis and the use of third-party eggs with conventional IVF.

She also suggests that the UK's "permissive record" on regulation "raises the prospect that inheritable mitochondrial changes would be used as a door-opening wedge towards full-out germline manipulation, putting a high-tech eugenic social dynamic into play."

She also believes that the long-term and pervasive impacts of even small genetic manipulations are unknown, and that it is "highly dubious" that these modifications would not "affect a person's identity."

Responding on SciLogs, Lee Turnpenny writes that some of Darnovsky's concerns about the safety of this procedure's outcomes are justified, but also that she has essentially engaged in a slippery slope fallacy.

First off, Turnpenny notes that Darnovsky is of the opnion that this mitochondrial replacement technology constitutes germline modification, making her article's title about a slope toward germline modification misleading.

Turnpenny distills the "slippery slope trope" Darnovsky uses as: "'Acceptance and moral justification of X will inevitably lead to, and automatically imply acceptance of, (undesirable) Y. Therefore, ban X.'"

However, Turnpenny says Darnovsky's central peg in the argument is not focused on whether this technology will lead to something "sinister," but asserts that the recommendation from the UK's Human Fertilization and Embryology Authority (HFEA) that further research is needed is the X that leads to mitochondrial replacement, or the Y.

"That, says Darnovsky, is the slope. Whether or not one agrees with her on that (and I think the invoking of eugenics, which is about state coercion, is not justified), she is justified in raising concerns about safety, what determining that safety entails, and of the apparent scope and conclusions of the HFEA consultation" Turnpenny says.