Two main types of genetic damage are recognized: chromosome aberrations and gene mutations. These may affect either somatic cells or germinal cells. Although damage to either cell population may have serious consequences, from the public health standpoint mutations in germinal cells are of paramount importance, as they present a hazard to future generations. The relation between the ability of a chemical to produce mutations in experimental test systems and its ability to affect humans is not firmly established but the potential hazard to the population is of great magnitude.
It is a problem for the human race that bacterial viruses can mutate, for it means that antibiotics are effective for only a limited time, until the virus has mutated to survive the drug treamennt.