Smoking effects on DNA. Animation showing the effects on DNA (deoxyribonucleic acid) of chemicals found in cigarettes. The animation starts with a man inhaling smoke from a tobacco cigarette. The animation shows the smoke entering the lungs. The close-up view shows molecules within the smoke, with the carcinogenic (cancer-causing) polycyclic aromatic hydrocarbon benzopyrene labelled. It is shown embedding itself in a strand of DNA. The clip concludes with the enzyme RNA polymerase (red) moving along the DNA strand during a process called transcription. The enzyme halts when it reaches the section of DNA that has been damaged by the benzopyrene. This type of damage to the cellular genetic machinery can result in cancer, in this case cancer of the lungs.