Quantum mechanics, which rules the world of the teensy-tiny, may help explain why genetic mutations spontaneously crop up in DNA as it makes copies of itself, a recent study suggests.

Quantum mechanics describes the strange rules that govern atoms and their subatomic components. When the rules of classical physics, which describe the big world, break down, quantum comes in to explain. In the case of DNA, classical physics offers one explanation for why changes can suddenly appear in a single rung of the spiraling ladder of DNA, resulting in what’s called a point mutation.