The Molecular Perspective: Ultraviolet Light and Pyrimidine Dimers

Abstract

Everyday, we are subjected to a powerful carcinogen as we go about our daily activities. Whenever we walk in the sun, ultraviolet light (UV) attacks our DNA, making chemical changes that corrupt our genetic information. Fortunately, the most dangerous UV light never reaches us at all: the ozone in the upper atmosphere absorbs (at least for now) the energetic UVC wavelengths. The longer UV wavelengths, however, do pass through the atmosphere and fall on us. The UVA wavelengths bordering on visible light, which are often used in tanning booths, are not energetic enough to modify DNA bases (although UVA may play an important role in formation of carcinogenic oxygen radicals). However, wavelengths in the intermediate UVB region are long enough to pass through the ozone but still energetic enough to attack DNA.