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Sat, 2005-Sep-10

Embryonic Nucleus Transplants

Jason Parker says "yay, science!" in regards to recent permission given to scientists in the UK to produce embryo with three genetic donors. I think the knowledge to do this sort of thing is valuable to science, and may lead to useful treatments for genetic defects in mitochondria. It is however not without ethical concerns. Reading Jason's post and some of the news articles available on the subject you may read this as being a technique to allow two women to have a baby together, each donating some part of their DNA to the mix. That is not the case. My understanding of this trial is that two embryo will be created with possibly two sets of parents (four individual donors). The nucleus of one embryo with its two genetic donors will be transplanted into the other embryo and its original nucleus discarded. The discarded nucleus contains DNA from both its donors, but the rest of the cell does not. The cruicial mitochondria that live outside the cell and act as power sources for all animal life are inherited from the mother only.

If you have moral objections to early term abortions, it would seem reasonable to have the same objections to this trial. Two embryos enter, one embryo (a combination of parts of the two) leaves. Views differ on this subject. Arguments range from "it is genetically human, so it is worth the same as a human life", to "it has the potential to be a human being, so is worth the same as a human life", to "it hasn't been implanted into anyone's womb, so doesn't really have the potential to be human life" to "it doesn't matter whether it has potential or not, it's just like any other cell or cluster of cells". Where you sit along that curve may guide your level of comfort or disquiet of the mechanics of the operation. Then there are the issues of what it is you are creating. These embryos will be discarded and will not implanted into a human womb. The end target of the research is clearly to make that happen using the same basic technique as they are attempting to master. Only if this happens will mitochondrial disease be cured.

Some ethicists would argue that it isn't "right" to alter human life at all. Francis Crick took an extreme alternative view and postulated that if humans don't seek to direct their own evolution then noone else would, so we would be foolish not to. Whichever way you lean it is probably reasonable from a neutral scientific viewpoint to say that despite the embryo continaing genetic material from three individuals that for all intents and purposes it still has a single mother and father. They are the donors who created the embryo who's nucleus was used in the transplant. Mitochondria is an essential building block of cell life but if functioning correctly does not contribute to hair colour, eye colour, intelligence, height, or any other trait that we could say defines a human in terms of its relations to the people around it. From this perspective the manipulation of mitochondrial DNA is a low hanging fruit both technically and ethically. It's easy to argue that only a part of the cell machinery and not the things which make a human human that are being replaced.

Genetic manipulation is technically and ethically a complex area of research. It is of untold value to understand genetics, but there are many mines to avoid tripping over along the way. What we accept today will be different from what our children will accept, and extrapolating one from the other is hard. If our children come to accept the creation and destruction of embryos without moral qualms and the manipulation of genetics as just a matter of recoding a computer program then they will see many technical benefits. The big questions of what is moral and whether slippery slopes exist in this area probably won't be answered until we have a more complete picture of what is actually possible and several lifetimes of experience in where the slopes lead.

Benjamin