Are you prepared to learn the secrets that your DNA holds?  Image courtesy of Wikimedia Commons.
Are you prepared to learn the secrets that your DNA holds? This image of color coded chromosomes is courtesy of Wikimedia Commons.

For the right person, an online genetic test can be both fun and useful. But for someone else, it might be overwhelming. Or even worse, reveal things they wish they hadn’t learned.

The tricky part is figuring out whether a genetic test that can trace your ancestry, reveal potentially deadly disease risks or even teach you about some of your physical traits is right for you. Probably the best way to find out is by talking to a genetic counselor. They’ve thought through (and probably seen) all of the side effects of a genetic test. But most people don’t do this.

Lots of people don’t even know about genetic counselors. The ones that do may not want to be bothered or even realize such a talk might be helpful. If you don’t have an inkling already about some of the pitfalls of a genetic test, why would you seek out counseling?

Another way that might help people decide if one of these tests is right for them would be to let them know what some of the unintended consequences of a genetic test might be. This is what we have tried to do with a set of animations we recently put up on our website. These short (less than two minute) animations are in no way exhaustive but they can give you a feel for a few of the potential pitfalls.

For example, in the second one you can follow Tina the genetics graduate student as she talks with a friend about the ancestry test she just had done. Her friend not only finds out about some unknown European ancestry, but she also starts to worry that the results mean that her dad isn’t related to her biologically:

Now in this case Tina’s friend’s results didn’t give any evidence either way about whether her dad was her biological dad (she’d need his results to confirm that). Still, the results were confusing enough that she needed reassurance from Tina.

And just because in this case the test didn’t show her relationship to her father, that doesn’t mean that these tests can’t sometimes reveal a dad who isn’t biologically related to his child. They can and they do. In fact, given that around 2% of men are in this situation, more and more people are going to find out their dad isn’t related to them (or that a sister is actually a half-sister and so on) as more and more people get tested.

In another scenario, Tina is talking to her sister about getting a BRCA test done because their mother got breast cancer at a very early age. People with certain DNA differences in their BRCA gene(s) are at a much higher risk of getting breast cancer in their lifetime. As you’ll see, during the conversation, Tina’s sister comes to realize that if Tina tests positive, then she has 50% of testing positive too (assuming Tina got the mutated BRCA gene from one of her parents). And that brings up some interesting consequences:

If Tina gets a positive result, should she tell her sister? If she does, then her sister will learn that she almost certainly has a 50% chance of having it as well. What if she didn’t want to know?

Of course this is a made up example (although people do deal with this problem all the time). Below is a video of a real life example of two sisters, Lani and Sherry, who decide to have a BRCA test because breast cancer runs in their family:

Now we see the sisters dealing with survivor guilt, anger and who knows what else. Luckily they had a genetic counselor to help them deal with these issues. Not everyone who takes an online test will.

We also deal with a couple of other situations too. In one scenario, Tina is trying to decide whether to get an online test to see if she is a carrier for the genetic disease cystic fibrosis. And in the other Tina is trying to decide whether or not to get a genetic test for Alzheimer’s disease. Neither decision is as easy as you think.

Don’t get the wrong idea, none of these are designed to say online genetic tests are bad and you shouldn’t take them. They can help you make informed choices like Angelina Jolie did recently when she tested positive for a DNA difference in her BRCA1 gene that significantly increased her risks for breast cancer. We wanted to make these videos so people could be introduced to a few of the potential pitfalls of these sorts of tests and so can make a better informed decision.

For example, I thought through these possibilities and none of them stopped me! I took a 23andMe test a few years back and couldn’t be happier. It was so cool to see the instructions for me written in the genetic code.

I can see the glitch that explains my red beard and when combined with a similar glitch from my wife, my son’s red hair. I can see the reason (well, one of them) for my blue eyes and the one for why I can’t taste the bitter chemical PTC and lots more. Heck, I even saw a hint of African on one of my chromosomes (although this was not verified with a second test from

The test also provided a huge amount of information about what my genes can tell me about my future disease risk. This is where someone who worries a lot might get very freaked out. Lots of diseases, lots of potential risk.

Since I have a background in genetics, I know to take most of this health risk data with a huge grain of salt. As a recent study showed, depending on the studies a company decides to include and the algorithm it uses to predict risk, you can end up with very different risks. Sometimes one company will say you are at an increased risk for a disease while another says you are a decreased risk.

So now it is up to you. Do you still want to take that online genetic test? After thinking it all through, I did.

  • Barry

    I forgot to include that these animations were created by a postdoctoral fellow, Hinco Gierman, a graduate student, Widya Mulyasasmita, and a genetic counseling master’s candidate, Sahil Kejriwal, as their final project for the Stanford at The Tech program:

  • Mars_Ultor

    Thank you for the article Dr.Starr. Can you recommend any good DNA analysis companies? Something for both ancestry and health analysis?

  • Mike

    Although genetic testing is a powerful tool I believe we lack the wisdom to use it, without consequences.

    In his book, Civilized Man’s Eight Deadly Sins” Conrad Lorenz outlines the root sources of the sins agains species survival. A reviewer States, “The sins are eight instances of wrong turns, ill-advised cultural choices which set our species on a course of development at odds with the rest of nature. Cultural selection is a tricky business, lacking the built-in controls of biological evolution and consequently able to wreak havoc on the environment, as we know, or produce a helpless, gross, aggressive mutant species of human being, which we’d prefer not to contemplate.”

    The application of genetic testing in human evolution without understanding the consequences ten generations down the road is like playing craps, where mother nature is the house. I’m not opposed the the use of genetic testing, just the use of it without understanding of the long term outcome, mans viability as a species. Without that understanding we run the risk of creating a human genetic cul-de-sac.


Dr. Barry Starr

Dr. Barry Starr (@geneticsboy) is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA and runs their Stanford at The Tech program. The program is part of an ongoing collaboration between the Stanford Department of Genetics and The Tech Museum of Innovation. Together these two partners created the Genetics: Technology with a Twist exhibition. You can also see additional posts by Barry at KQED Science, and read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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