Let’s say you are a young person thinking about having a baby, but you know there is a genetic disease in your family that worries you. It’s a reasonable concern that people have recognized for some time. There have always been diseases to concern parents, but technology is changing how we think about and face these concerns.
Once upon a time these was little more to do but cross your fingers and hope for a good result. Then chromosomal testing (Karyotyping) of a developing fetus became possible allowing parents to know what is happening inside the womb. Getting this information was not without risk, and even with the results in hand, would-be parents are faced with terrible choices. The way we dealt with this test in our family was to not have it done. We really wanted a baby and thought that that having test results would not change our behavior. So we chose not to be put in a position of having to make that choice. It was what worked for us, but we also didn’t have specific concerns other than the fact that we were getting older.
Following the advent of chromosomal tests, it became possible to test the DNA of a fetus for specific, known problems. For example, If caner runs in the family, you could check to see if the baby’s p53 gene was normal. Having one or more bad copy of this gene dramatically raises the probability of developing cancer relatively early in life. Today, this is something we can know for certain.
But there are several sources of DNA in us. We typically think of the vast amount of DNA carried in the form of linear chromosomes that are packaged inside the nucleus of our cells. This is definitely the lion’s share of the DNA passed from one generation to the next, but there is another source as well: The Mitochondria. You may have learned about these organelles (little organs) as the ‘Powerhouse of the Cell’ for its role in generating much of the energy (ATP) your cells need to do their jobs. These organelles have a strange history in us. It is thought that many eons ago those things that are now mitochondria inside our cells were once free living organisms (possibly parasites, possibly a bigger cell’s dinner). However it happened these microbes were taken inside of our cells, but not digested as food or harmful enough to kill the host either.
Why am I talking about this? Because those organelles still carry remnants of their former selves. They still have their own protein-making machinery and even their own DNA. This DNA isn’t large, but it does carry genes coding for vital proteins. And this is how we get back to our original story, because sometimes these mitochondrial genes are no good. If these genes aren’t right, they can’t make healthy, functional proteins. If they can’t make good proteins, then the host cell and the while organism can die.
Interestingly, all the mitochondria in every cell of your body came from your mother. This is one place where dad makes no contribution. Even though sperm have mitochondria, they don’t get incorporated into the new zygote, only those from the egg will remain.
Enter The Future of Fertility Medicine
Recent developments have shown that it is possible to replace the unhealthy mitochondria with healthy versions from a donor cell to make good eggs that can be fertilized and result in a healthy child. This was the subject of an excellent review in Nature and also discussed on the Nature Podcast this week. So how many parents is that? One mom, one dad and one mitochondria donor (I guess this could conceivably come from dad, but I just don’t know). This procedure has been done successfully with non-human primates, but so far not with humans.
So, pursuing a simple line of work aimed at helping parents make healthy babies is suddenly possible and suddenly a great ethical question. Have you ever seen Gattaca? If not, go out and watch it. I was sure this film was going to be miserable and be a poor representation of science, but I was totally wrong. They ask the same questions in that film that we are beginning to face in real life:
When does Medicine become tampering with life? And does it matter? Don’t we want healthier, more able bodied people? Is it wrong to replace bad genes? What constitutes ‘bad’?
Personally, I don’t believe that there are universally right and wrong answers to these questions. Even if we decide that there are some less desirable consequences for mankind, that doesn’t mean that we wouldn’t do it. Much of plastic surgery isn’t really necessary and some might call it a perversion of medicine, but that doesn’t stop tons of people from getting it.