Lifespan: The Revolutionary Science of Why We Age—and Why We Don't Have To

by David A. Sinclair

Every one of our cells has the same DNA, of course, so what differentiates a nerve cell from a skin cell is the epigenome, the collective term for the control systems and cellular structures that tell the cell which genes should be turned on and which should remain off. And this, far more than our genes, is what actually controls much of our lives. One of the best ways to visualize this is to think of our genome as a grand piano.13 Each gene is a key. Each key produces a note. And from instrument to instrument, depending on the maker, the materials, and the circumstances of manufacturing, each will sound a bit different, even if played the exact same way. These are our genes. We have about 20,000 of them, give or take a few thousand.14 Each key can also be played pianissimo (soft) or forte (with force). The notes can be tenuto (held) or allegretto (played quickly). For master pianists, there are hundreds of ways to play each individual key and endless ways to play the keys together, in chords and combinations that create music we know as jazz, ragtime, rock, reggae, waltzes, whatever. The pianist that makes this happen is the epigenome. Through a process of revealing our DNA or bundling it up in tight protein packages, and by marking genes with chemical tags called methyls and acetyls composed of carbon, oxygen, and hydrogen, the epigenome uses our genome to make the music of our lives.

Epidewort is the maestro of the piano '