In time there may be millions of such altered cells. This latter mechanism, called biological magnification, can cause some of the chronic diseases and changes we usually associate with old age. One very specific mutation which can occur within the cell is the destruction of the cell's mechanism for resting which normally causes it to cease reproductive activities after cell division. This inability to rest results in a runaway proliferation of cells in one place, which, if not destroyed, will form a tumour, either benign or malignant. If the radiation damage occurs in germ cells, the sperm or ovum, it can cause defective offspring.
Radiation can also damage an embryo or foetus while it is developing within the mother's womb.
This is called teratogenic damage, or the child is said to have a congenital malformation rather than genetic damage. This means the damage is not automatically transmitted. The damage done within cells by random releases of the energy of photons, alpha, beta or neutron particles can occur indirectly through an effect called ionisation. As the energised photons or particles speed through the cells, they give energy to the electrons of chemicals already within the cells, enabling some electrons to break free from the rest of the atom or molecule to which they are attached. On the macro-level this would be comparable to an atomic explosion of a magnitude great enough to drive the earth or another planet out of its orbit around the sun.