And yet, to add to the complexity inherent in genetics, the central dogma in some cases is true. For instance, there are rare genetic mutations -
glitches in critical sequences of DNA - that are directly responsible for diseases such as Down syndrome and Tay-Sachs. For these terrible and usually
fatal conditions, single mutations are highly predictive.
For most common diseases, however, this has not turned out to be the case. The impact of single genetic mutations in auguring risk factors for, say,
diabetes and many cancers, is at best only slightly more informative than knowing one's average risk for these maladies.
This is the point of the study published last week in Science Translational Medicine, which looked at the predictive power of genes for 24 common diseases. Researchers at Johns Hopkins studied the
genetics and the outcomes of over 53,000 twins born with identical DNA. They discovered that for 20 major diseases the genes had little or no extra
This is what the headline above reports, which seems like a victory for the "genes are overhyped" camp. Yet the news here is also more nuanced. It
turns out that for the four other diseases analyzed by the Hopkins team - Alzheimer's disease, autoimmune
thyroid disease, Type 1 diabetes and
heart disease for men - genetic tests can identify up to 75 percent of those who will get these diseases.
Neither does the headline above about new gene mutations for autism tell the whole story about that discovery. As the Times story under the
headline explains, the newly identified mutations - made by three different teams at Yale, Harvard and at the University of Washington in Seattle and
reported in Nature - are extremely rare, impacting only a handful of patients. Nor do they seem to have much
relevance to diagnosing, treating, or predicting autism, though the researchers believe the discoveries could be important for better understanding
mechanisms of the disease.
While I was writing my recent book, Experimental Man, and after its publication, scientists identified over 23,000 personal genetic risk factors for me - everything from a low risk of having brown eyes (true: my eyes are blue) to a high risk
for Parkinson's disease (false: at age 54 I thankfully do not have any sign of this condition). Other risk factors suggest a high probability that I
will suffer side effects from certain drugs, such as statins, which I will keep in mind should my cholesterol soar.
Otherwise, my vast library of possible genetic futures has not changed my life - in part because I'm not sure what to believe given the current
dialectic of genes as vital predictors to some and as overblown to others. I expect this to change as interpretations of personal genetic traits
improve, but this remains in the future.
Nor does it make sense to emphasize the augurs for the future in our DNA when they are just part of the equation telling us what is happening, or might
happen, to our bodies in time. Other factors include the impact of our environment - what we eat and chemicals we are exposed to - and also what is going
on in certain proteins in our body.
The sooner we normalize the storyline about DNA, the faster genetics will take its rightful place in our science and in our imaginations as one of
several remarkable and critical elements that make us who we are - and what we might become in the future.