By Sarah Zhang
As you read this article, the cells in your body are dividing and the DNA in them is being copied, letter by letter. So long is the human genome—more than 3 billion letters—that even an astonishingly low error rate of one in many million letters could amount to 10 new mutations every time a cell divides.
Oh, perhaps you’re also catching some sun (ultraviolet rays) while you read this, or enjoying a beer (alcohol), or have recently been high in the atmosphere on an airplane (cosmic rays). Congratulations, you’ve given yourself even more mutations. In a typical day, scientists estimate, the 37 trillion cells in your body will accumulate trillions of new mutations.
Are you horrified yet? Good, me too.
But somehow we are not all walking bags of cancer. Somehow we accumulate bajillions of mutations and are, mostly, okay. How?
“It sounds very scary,” acknowledges Cristian Tomasetti, a cancer researcher at Johns Hopkins. “Fortunately for us,” he says, “the great majority of places where these mutations may hit don’t have important consequences.”
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