DNA damage from radiation. Animation showing damage to a molecule of deoxyribonucleic acid (DNA) by ionising radiation from radioactive isotopes. A worker at a nuclear facility handles radioactive material. The decay of the unstable radioactive isotopes (red and yellow) produces ionising radiation (green wave). If this radiation penetrates the protective clothing, it causes damage to DNA. DNA is composed of two strands twisted into a double helix. Each strand consists of an outer sugar-phosphate backbone (grey) with nucleotide bases attached (guanine (G), cytosine (C), thymine (T) and adenine (A)). The ionising radiation damages a section of the DNA, breaking the sequence of nucleotide bases. This is damaging to an organism because DNA contains sections, called genes, in which the specific sequence of bases encode the body's genetic information and determine each cell's structure, function and behaviour. Extensive doses of ionising radiation are dangerous as incorrect repair by the body may lead to cancers and other abnormalities in the individual.