12 September 2005

Heather has two mommies — and a daddy

You've probably heard about the embryo that's been proposed, using a fertilized egg cell from one mother, but a nucleus from another couple's fertilized egg. This would give the embryo genetic material from three parents. The nuclear DNA is half from the father and half from one mother, in the usual way, so what does the third parent have to do with this?

It turns out that mitochondria have their own DNA, which we inherit from our mothers. The speculation is that mitochondria were once free-living organisms which were "captured" by our very early unicellular ancestors. The mother from whose egg the nucleus would be taken could have a flaw in her mitochondrial DNA, which causes a muscle disease. The Franken-egg is part of a research project to see if it would be possible for a mother with this disease to have children who are free of it.

Now, the reason I'm interested in this is that I have a close relative who has a mitochondrial myopathy — in fact, he's the only person known to have his particular form of it. And the reason I recently had a muscle biopsy was because of the possibility of this disease in me.

I'm going to guess that the research will eventually find that the mitochondria and the rest of the cell, even if, long ago, they were independent, have become somewhat more entangled with one another over the eons, and that allowing such an embryo to reach maturity would make those dependencies manifest, just as cloning has revealed DNA to be more complex, and more dependent on the cellular environment, than was once assumed.

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