Inheritance: How Our Genes Change Our Lives—and Our Lives Change Our Genes
Sharon Moalem
Grand Central Publishing, 2014
Imagine you are at a dinner party with your spouse, but you can't keep your eyes off the host, enthralled as you are by the curve of her neck. For many, this might warrant a heated spousal talking-to. And so it does for Moalem, a specialist in rare genetic disorders, though not for the reasons you might think.
For Moalem, certain features—the cleft of a chin, the space between eyes, even extra eyelashes—may signal rare developmental and genetic diseases. In this case, to Moalem, the web of skin between neck and shoulder suggests Noonan syndrome, a disorder associated with heart defects and other problems. (He later discovered his suspicion was correct.)
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As Moalem details in his new book Inheritance, the study of rare genetic diseases serves an important purpose. These disorders, which usually stem from mutations in a single gene, give scientists a better idea of what that gene does. These clues are important not just for treating carriers of the mutations but also for understanding other diseases. For instance, a mutation in a receptor for growth hormone causes an extreme shortness called Laron syndrome. Those with the syndrome are unusually resistant to cancer. This inverse association, which suggests a link between growth hormones and malignancy, points the way toward new potential cancer treatments.
Genes are often turned on and off, up or down, not by mutations, it turns out, but by environmental factors. Which brings us to the central thrust of Moalem's book: genes may be immutable, but how they are translated into flesh and blood absolutely is not.
Consider the honeybee. The only difference between a hive's queen and the sterile worker, both of which have the same genes, is diet. If a bee larva gorges endlessly on royal jelly, it matures into a queen. If it consumes just a few days' worth of jelly, it becomes a worker.
Mammals are not so different. Make a mouse pup anxious daily by removing it from its mother, and it becomes prone to a rodent form of depression in adulthood. Here is the kicker: pups born to this tormented animal inherit the same depressive tendency, even without experiencing the original torment. The transmission occurs not by genetic mutation but by epigenetic modification—the silencing or unsilencing of genes. This is how “our lives change our genes,” which is both an empowering and, if our lives are not so great, frightening concept.
One of the more surprising takeaways is that the long-promised era of personalized medicine—where doctors tailor treatments to your particular genome—is arriving piecemeal. Currently available tests can detect important genetic variants. One variant prevents carriers from breaking down the sugar fructose, which can become hazardous if these individuals consume too much fruit. Despite their usefulness, such tests are not necessarily routinely conducted.
Inheritance is a wide-ranging and breezily written survey of an immensely important field—the science of how we may “tweak” our fixed genetic heritage to produce health and well-being. The narrative moves quickly, and what the book lacks in depth it more than makes up for with breadth, providing a solid foundation for readers. It is especially thrilling for a geneticist, of all people, to emphasize “it's not only what our genes give us that's important, but also what we give to our genes.”