When 23andMe offered their DNA test for just $99, I started to think about giving it for Christmas presents. It was an easy decision to send one to my dad (although I’ll be curious to see if he’ll do it). What was much trickier was deciding whether to give one to my 15 year old son.
There are a number of reasons I wanted to give away this test to my relatives. The first is that I want to see how the DNA got passed down from my dad to me. And how it got passed from me to my son.
You might recall that we all have 23 pairs of chromosomes. We get one of each pair from our moms and one from our dads.
When we pass this DNA down to our kids, the DNA in each pair goes through a process called recombination. This is where DNA is swapped between the two chromosomes in a pair. The end result is that the chromosome 1 that I got from my dad is a mix of his two chromosome 1’s. The same is true for the chromosome 2 that I got all the way through chromosome 22. (The Y I got passed pretty much unchanged.)
It would be so cool to see this in action with my own DNA. Seeing a concrete example of something that has largely been theoretical up to this point somehow makes it more real. Especially with my own DNA.
At least this was the case when I got the whole family tested for the gene responsible for most cases of red hair, MC1R. It was so satisfying to see that my wife and I were carriers for red hair, that we each passed a red version of MC1R to our red haired son, that our older son got one copy and so was a carrier like us and that our daughter didn’t get a red MC1R gene. Even though I knew my wife and I were carriers and out red haired son had two red copies, it seemed more real once I saw the genetic results.
The test can also tell us something about our ancestry. For example, it was cool to see that the tip of one of my chromosome 11’s actually comes from an African ancestor. I am 0.1% African. How cool is that?
Getting my dad tested would tell me if I got that from him. Undoubtedly I did as his family is from Arkansas and my mother’s is from Berlin, Germany but still it would be nice to confirm. My dad’s DNA could also tell us whether an old family legend about us being related to the outlaw Sam Starr is true.
See Sam Starr was half Native American which would mean we would have some Native American DNA too. As I talked about in a couple of previous blogs here and here, I couldn’t see Native American in my own DNA. One reason for this might be that I am one generation too far for the test to be able to see that DNA in mine. Maybe since my dad is one generation closer, we could see the Native American DNA in his.
OK, that was the fun stuff. Now on to why I might be hesitant to get my son tested. It has to do with what our DNA can and can’t tell us about our future health risks. And how these findings are packaged.
One of the things you can quickly learn is whether you are a carrier for some deadly genetic disease like cystic fibrosis. They don’t test for every possible variant so a negative result may give a false sense of security. Still, it would be good to know about the common ones, right? I guess maybe…
This kind of knowledge is important for my son to know once he’s married but does he need to know about his genetic burden now? Is he ready for it?
And what about straight up genetic diseases? I found out I am a carrier for something called hemochromatosis. If my wife is one too then my son has a chance of getting the disease although even if he got the "bad" versions from my wife and me he still only has a chance at the disease. (Hemochromatosis is incompletely penetrant.)
At least with this one there is an easy remedy if you end up with it. You just have to give blood often and you are OK. But what about diseases you can’t do anything about?
Imagine he finds he has two copies of the APOE4 version of the APOE gene. These people are much more likely to end up with Alzheimer’s later in life. Should a 15 year old be subjected to that worry for the rest of his life?
Now that one is only theoretical. Because I have two copies of the “good” version of APOE, APOE2, I know at worst he’d have a good and a bad version (APOE3 is the neutral version). Of course then my wife would know she probably carries at least one APOE4 and now she can start to worry. And maybe feel bad that she passed it on to her son…
The list of issues like this goes on and on. I haven’t even dealt with things like DNA differences that led to a 1.5 fold increase in prostate cancer or macular degeneration or who knows what else. Is he ready to get that kind of information and, more importantly, to understand the limitations of the information?
For example, just because he has a marker that more people who ended up with prostate cancer had, that doesn’t mean that the marker means the same thing in him. His genetics are his own and everyone will have a different risk for these sorts of multi-gene traits. And even if he is twice as likely to get brain cancer, does he know what those numbers mean? Or will his lack of understanding make him depressed because he thinks he will most likely end up with brain cancer? Yikes.
To test out how ready he was, I decided to share some of my results with him while my eleven year old daughter listened in. First I showed them the ancestry and traits like lactose intolerance. They thought these were very cool (and they were right). I also showed them how my DNA showed that my blood type probably was A+ and that I was a carrier for O and Rh negative blood type. We got into a nice discussion about what that means for them. Neat.
Then I moved onto the disease section. This is where things started to get ugly.
I learned pretty quickly that my daughter did not have the right personality for these sorts of tests (at least not yet). She focused in on the various diseases, learning all the ways I could one day die and started to get very worried. I tried to use my understanding of genetics to tell her that these are just risks, they aren’t a for sure thing but I was getting nowhere. She tends to worry a lot and this simply gave her more to worry about. Hopefully she will forget about this and move on.
My son was a different matter. He was very interested in things without worrying too much but he was taking some of the health things too literally. For example, my results showed a significantly increased risk for late age macular degeneration (a nasty eye problem). Scary.
Except that again, this is the average risk of lots of people with varying genes who share this marker. My own risk is my own and is dependent on lots of other genes (and the environment!) besides this one. So basically I take these results with a grain of salt, waiting for more data to see if it is meaningful or not.
But he homed in on these results and decided they were set in stone. He saw a bunch of yellow stars that indicated that 23andMe was very confident in this result and so assumed that that meant they were very confident that I had the chance for this disease they quoted.
I explained that this is not the case. 23andMe has a great deal of confidence in the study itself but not necessarily in its predictions as they related specifically to me.
In the end I didn’t get my son the 23andMe test. I wish they offered some way to just look at some of the data and not all of it at once. Then I might have given this as a gift to my son and maybe even my daughter.