While all the hype about getting your genome read is centered on discovering your geographical origins, learning which parent you got your personality from, and becoming aware of your various predispositions, there could be some negative consequences from getting your genome sequenced. A professor at Princeton University recently asked me if I was mentally prepared for the worst with my DNA test. At first I wasn’t sure what he meant, but after some brain storming and a bit of research to back it up, I have come up with the 5 worst things to learn from reading your chromosomes:

5. Your family is not from where they claim to be from:

If you walk into a classroom of average 5th graders in the United States and pose the question, “What nationality are you?” you can expect a range of answers. “Irish and Italian” might answer one young-un. “One-fourth German, One-fourth Dutch, and Half French” will claim another. Due to the cultural importance placed on ancestry in the United States, these kids will leave out the obious answer of U.S. Citizen.

Using your own genetic data along with the information from the HapMap Project, it is possible to determine the geographic origin of haplotypes – groups of associated SNPs – in your genome. For children and adults that have paraded around with the Italian flag their whole life, or those who don’t leave home with out their “luck of the Irish” jacket, it would be world-crushing to discover that instead, your genes come from France, or China.

4. You are at higher risk for cancer/alzheimer’s/heart disease/diabetes/etc.

While you may feel healthy now, it is possible that you might discover a bleaker future awaits you. Everyone is at riskfor developing certain diseases, but some genes greatly increase the chance of developing these maladies.

There is some fear that genetic risk factor information may cause people to react in an extreme manner. While the data from each individual study is statistically sound, their combined effects on each individual have not been tested. Should their values be added, or should they be multiplied?

My only word of caution with risk factor information is don’t feel like you need to go bungee jumping and skydiving to make sure you get your ‘last big thrill’ anytime soon. There is still much research to be done on exactly how each particular SNP is associated with the onset of each disease.

3. You were adopted…or perhaps there was a mix-up at the hospital

For families that get their genes read together, it is normally possible to see which part of a child’s chromosome comes from which parent (or grandparent even). In the event that a child’s DNA has very little overlap with either parent, it is evidence that they are not quite related (in the familial sense). Perhaps the parents were keeping an adoption a secret from the child?

Of course, there is an alternative hypothesis in this situation. Although not terribly common, it is a fear of new parents that their new baby might be accidentally swapped for another newborn. Last year, two Czech couples discovered that they had raised each others’ daughters for 10 months before deciding to swap back. If a DNA test reveals that a child’s genes don’t match the parents’, maybe there was a hospital mix-up!

2. Your father is not your real dad

While maternity is generally not disputed (with rare exceptions) since a mother physically gives birth to her child (again, not in all cases), paternity can sometimes be dubious. If a child gets tested and discovers that there is significant overlap with his mother’s genome, but very little with his father’s (or perhaps the child sees that the geographic origin of his DNA does not match his father’s), then it may suggest an extra-marital affair. Although some information found from these genetic tests may be trivial, this certainly qualifies as life-altering material. Cheaters beware, you can’t hide from science.

1. Girls: You may not be a girl…genetically at least

That’s right. Girls might discover that they are genetically males. Every person has two sex chromosomes (again, there are some exceptions). Girls have two X chromosomes, while boys have one X, and one Y chromosome. However, a rare genetic variation known as Andogen Insensitivity Syndrome (AIS) causes XY individuals (normally male) to develop a female external appearance.

Complete AIS generally results in external female development with internal testes. This information is definitely a life-changer. See this ABC special on AIS:

So there you have it. Not everything you discover during your commercial genetic test is going to be candy and unicorns. There could be some serious information, and perhaps some life-changing information. While I still maintain that there is significant value in being aware of your predispositions, knowing the possible worst case scenario will help you proceed with caution.

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