All living cells, whether microbes, plants or animals, contain a complex molecule called DNA which carries the genetic code. This is the set of instructions which describes the structure and biochemistry of an organism. Unfortunately, DNA readily absorbs high-energy UV-B radiation and becomes damaged so that the instructions cannot be read properly. If the amount of UV-B entering the cell increases (as during the ozone hole), the risk of damage also increases and may result in malfunction or death of the organism. Some Antarctic organisms such as algae, lichens and mosses, also contain a pigment called chlorophyll. This absorbs visible light as the energy source of photosynthesis for making organic compounds. Chlorophyll also absorbs UV-B light so that the system becomes bleached and non-functional. Even enzymes and other proteins are damaged by this high-energy radiation. Living organisms therefore have to protect themselves from UV-B. Humans can cover their skin with artificial sunscreens, but natural protection systems have also evolved. Many microbes, plants and other animals synthesize protective pigments. Our skin cells synthesize brown melanin to protect against sunburn (which is caused by UV-B radiation), and so do Antarctic lichens on rocks near the edge of the polar ice-cap. A variety of sunscreen pigments are produced by Antarctic organisms on land, in freshwater and in the sea. That is why exposed, snow-free rocks are often covered with bright orange and yellow lichens. Some lichens and microbes even live inside translucent rocks to shelter from high radiation levels and desiccating winds!