If the energy of an incident particle is sufficiently high it can displace an atom from its position in a molecule. In extreme cases a cell could be killed outright, but there are more subtle forms of damage. Altering a DNA sequence that controls growth may cause the cell to grow without limit. When such a cell divides it passes this faulty sequence on to its progeny. A group of such damaged cells that divides without regard to the health and well-being of the body as a whole is called a tumor and an animal afflicted with such a condition is said to have cancer .
Nuclear radiation is said to be mutagenic in that it can damage or mutate the genetic code of cells.
Since these mutations may also lead to cancer in animals, it is also said to be carcinogenic or cancer-causing. The forms of radiation that are especially dangerous to living things are those with energy sufficient to penetrate tissues and then ionize the atoms they pass along the way. 1 MeV. They damage tissues by disrupting normal cellular chemistry. The amount of energy absorbed from a source of radiation by some material per mass is called the absorbed dose . It is a quantity that applies to any source of radiation acting on any type of material, be it living or non-living.