BEYOND INHERITANCE

Dynamic DNA.

Evolution has shaped, as Charles Darwin put it, all the “endless forms most beautiful and most wonderful” of living things. But he did not know that the trillions of cells in our bodies also compete among themselves, with massive consequences for the cells and often for us. The structure of DNA has been known only since 1953. The human genome sequence wasn’t published until 2001. Not surprisingly, then, science is still making discoveries in genetics. This well-researched volume by science journalist Khamsi examines the recent appreciation that each of our particular genomes is subject to numerous and accumulating mutations during our lifetimes—often inconsequential but sometimes vital for the individual walking around with that genome. “When people talk about genetic diseases,” Khamsi writes, “they are typically referring to inherited ones.” Sickle cell is a classic example. But now we know that cells with mutations that start in a single cell in the developing fetus, or even after birth, can reproduce and outcompete “normal” cells to cause a different kind of genetic disease. Although cancer is a well-known disease of non-inherited mutations, newer studies find numerous other such conditions: Examples include some cases each of endometriosis, a heart condition called long QT syndrome, and epilepsy. In perhaps the most fascinating chapter, Khamsi explains how acquired mutations can alleviate devastating conditions. Two boys afflicted with the rare immunological disorder known as “bubble-boy disease” seemed doomed to live sheltered from infectious threats within plastic enclosures. But they spontaneously improved, apparently because a single cell sustained a beneficial mutation after which progeny cells outcompeted the boys’ faulty cells. Even trees get in on the act. A eucalyptus in Australia was decimated by beetles—except for one branch that analysis revealed had developed multiple mutations that saved it. Such cases offer hope for future therapies.

“There is grandeur in this view of life,” Darwin said of evolution. Grandeur also exists in this new view of DNA.