Maria Spies tells “single molecule stories” in DNA biochemistry. She describes what happens when DNA helicases, molecular motors that drive DNA repair, find breaks and “hot spots” in DNA or encounter other proteins bound to the DNA molecule. Spies uses DNA helicases that are linked to breast and ovarian cancer and to rare genetic disorders involving premature aging, stunted growth, and a dangerous sensitivity to sunlight. DNA repair is vital to all cells. By one estimate, every cell in the body must undertake 190,000 DNA repair events every day to keep up with the damage inflicted by ultraviolet light, toxic chemicals, and the dangerous by-products of normal metabolism.

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