DNA damage. Computer artwork of damage to a molecule of deoxyribonucleic acid (DNA) by ionising radiation. DNA is composed of two strands twisted into a double helix. Each strand consists of an outer sugar-phosphate backbone (blue coil) with nucleotide bases attached (guanine, cytosine, thymine and adenine). The ionising radiation (energetic particles or waves, yellow) is seen to be breaking these bonds apart. This is damaging to an organism because DNA contains sections, called genes, which 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.