Map of life expectancy at birth from Global Education Project.

Friday, April 10, 2015

Land of the Free and Home of the Benighted


I don't know if you've heard of mitochondrial replacement therapy (MRT), but it's legal in the UK and not in the US. Why is that?

So, first a bit of biology. This will make more sense to you if you are not a creationist. Somewhere back in the mists of time -- long before the universe was created 6,000 years ago -- actually somewhere around 2 billion years ago, it seems that 2 (or possibly 3) simple prokaryotic cells entered into an endosymbiotic relationship. We don't know exactly how this happened. Prokaryotic cells don't have a nucleus and are otherwise relatively simple in their internal structure. There are two major kinds, called archaea and bacteria. The most straightforward explanation of the origin of the eukaryotes is that an archaeal cell somehow engulfed a bacterium, but didn't digest it. Instead, the bacterium reproduced and its progeny started living happily within the cytoplasm of the archaea and its descendants. The endosymbiotic bacteria gradually lost most of their DNA -- they didn't need it because their environment was properly managed by the archaeal DNA, which is now our nuclear DNA -- and they settled down to a few jobs, including the production of adenosine triphosphate (the cell's fuel) and some other essential functions.

The eukaryotes went on to evolve and produce the metazoa -- that's the animals, including us -- and plants, which evidently absorbed another prokaryote, which happened to be photosynthetic, and is today the chloroplast of the plant cell. Anyhow . . .

Some people have defective mitochondria. These can only be inherited from the mother, because the cytoplasm of the ovum becomes the cytoplasm of the zygote. Got that? The sperm don't contribute any mitochondria to the embryo. Having defective mitochondria can be a real bummer. Because mitochondria perform various functions in various tissues, and at different times of life, the manifestations of mitochondrial disease are myriad.Anyhow . . .

These diseases aren't curable, but it is now possible for a woman with defective mitochondria to give birth to a healthy baby. There are actually two ways to do it, not much to choose between them really. Method A is that you produce an ordinary zygote by standard in vitro fertilization, then you take a donor oocyte from a woman with healthy mitochrondria, remove it's nucleus, and insert the nuclear from the zygote. Presto, you have mommy and daddy's nuclear DNA in cytoplasm containing healthy mitochondria. Note that the only characteristic the baby will inherit from the egg donor is healthy mitochondria. Otherwise, the baby will be just like any other baby of those two parents -- each of them has contributed half of the DNA that makes us who we are.

The other method, which as I say is six of one, half dozen of the other, is to replace the nucleus of the donated oocyte with the nucleus of an oocyte from the mother, and then fertilize it. Doesn't matter.

It turns out that people in the U.S. find this ethically unacceptable. Some of them don't get past the "three parents" weirdness factor. That really isn't true, but lot of corporate media reports just say it is because the reporters are ignorant.

The other reason is because people seem to think that method A constitutes abortion. Really. I mean, you have a zygote, which as far as they are concerned is already a baby. Note that it isn't even a blastocyst. Part of it -- the cytoplasm -- is destroyed, even though the nucleus goes on to make the baby that otherwise would have happened, only healthy. They would rather have a sick baby than toss away that microscopic bit of slime. Because Jesus said so.

Ponder that.

2 comments:

Elizabeth Ring said...

I had not heard of this technology, but thank you for the explanation. I always feel weary when I hear of the religious and pro-choice's arguments against technology which have the ability to foster a HEALTHY new life, instead of a defective or ill new life. There never seems to be any argument against the technology that improves an existing life: pacemaker, stent, artificial valve, artificial limb, etc. Why so much resistance about being proactive and getting it right from the get-go???

Cervantes said...

Well, there is definitely a legitimate debate to be had about the prospect of modifying the germ line of nuclear DNA, e.g. modifying genes to make smarter or more athletic or better looking babies.

But this is not that.