I recently saw a 50-something year old man for a cancer genetic counseling session. When we got to the concept that mutations in the BRCA genes may increase someone’s risk to develop breast and/or ovarian cancer, he was amazed. He said to me, “If the technology exists for someone to know his or her genetic risk to develop cancer, and there may be something to do to reduce these risks, wouldn’t it make sense to learn this information when someone is young?”
I was pleased to hear this question since it proved to me that he was really paying attention, and although he didn’t realize it, he touched on an issue which is very timely in the world of genetics and ethics. The issue of whole genome sequencing (reading through all of someone’s genes to look for variation) is a hot topic in genetics. Currently, the reasons we might order any genetic testing are if there is an underlying medical issue for the individual, a family history of an issue, or if someone is from an ethnic group that has known founder mutations for particular diseases. When we do this sort of testing, we are looking for relevant mutations in one or more genes or chromosomes.
But recently, scientists have introduced the notion of testing the entire genome of all newborns-even those who are seemingly healthy. (Note: I am not talking about the Newborn Screening panel—AKA “heel stick test” or “PKU test”—which is mandatory in the United States, and tests for about 30-55 diseases, depending on the state). And to make things sound even more exciting, the first baby to ever have his genome sequenced prenatally was born last month in California!
Back in November 2012, Nicole blogged about her discomfort of whole genome testing, as opposed to targeting the genetic testing to the medical issue at hand. When we do whole genome sequencing, we are going to learn about that person’s traits, carrier status, predispositions to childhood and adult-onset disease, and we may even diagnose a disease, possibly presymptomatically (ie- before the person even starts exhibiting symptoms). Some might think that all this information is great, since it’s better to know now than to be surprised when it happens.
Others believe that this type of testing for newborns is unethical. Here are a couple of reasons why:
1-The genes belong to the child, not the parents. Shouldn’t it be up to that child to make this decision?
2- Say we learn that the child is genetically predisposed to having Parkinson’s disease. This most likely will not happen for another 50 or so years, and it may never happen at all. Does he want to be that person who is just waiting to get sick? This may cause anxiety, stigma, and may change the way his family and friends perceives him.
3- If someone learns from a young age that he has a genetic predisposition to a condition, he may ignore the other (non-genetic) risk factors. For example, let’s say someone learns that he has a genetic variant that leads to a high chance of developing diabetes. He may not try to eat healthy foods or exercise or go for checkups because he believes that his genes alone will determine his risk for diabetes. This is what we call “genetic determinism.”
I told my patient that he did not realize that he had opened up a can of worms and that we would need a whole new session just to discuss his question. But he definitely got me thinking.
Genetic testing is complicated. No really, it is! Since the concepts of genetics and genetic testing are so abstract for most people, coupled with hearing about all of these new and fancy genetic technologies, people assume a simple genetic test can tell you just about anything. Unfortunately, it can’t. Here are a few things about genetic testing which will hopefully set you straight.
1) We cannot prenatally test for intelligence, height, hair color, or athletic ability. We cannot create designer babies either. This comes up a lot when we think about the ethics of prenatal testing and the fear of eugenics. We can’t test for, or manipulate these traits because we don’t know the gene, genes, combination of both genes and environmental factors which contribute to their development.
2) Prenatal testing at this point is limited to things which are common, or known. We can test your unborn baby for Down syndrome (caused by 3 copies of chromosome 21), or other chromosome abnormalities. However no matter how much testing we do, we cannot test for mental retardation, autism, or even rule out the possibility of any genetic diseases or problem. This is primarily because, as I mentioned before, we don’t know the cause or causes of these things. If there is a specific genetic disease in your family where the gene and mutation has already been identified, we CAN test your baby for that. However when it comes to prenatal genetic testing, we are limited to only being able to test for things when we know EXACTLY which gene we’re looking for, and many times, what specific mutations we’re looking for within the gene.
3) While we can sequence your genome, we can’t really tell you what it all means, yet. As perhaps you have been starting to see, for all that we do know about genetics, we still don’t know a TON. Genetics, and the interplay of our genes and environment are much more complex than you might expect. And in addition to the genes which we know of in the body, there is a large amount of regulatory regions which affect how those genes are expressed. Even the environment can affect how our genes are expressed. Without fully understanding the interplay between our genes, the regulatory regions of our DNA, and our environment, we can’t fully understand and explain the full implications of the genetic “sequence.”
4) Genetic testing does not consist of one “catch all” genetic test. There is no one genetic test which can tell you everything you’ve ever wanted to know about your future health risks, medical issues for your kids, and if you’ll develop cancer in the future. When we do genetic testing, we test usually one specific gene, sometimes even a panel of genes, based on the particular symptoms or family history. That’s why the process of genetic counseling and genetic testing is so thorough. We assess your medical and family history to determine which genetic test should be ordered, since after all, you do have thousands of genes and we aren’t testing them all at once.
At least not yet.