The Role of Genetic Factors in the Aging Process1

years ago it was shown (Stevenson & Curtis, 1961) that chromosomal aberra-tions develop in liver cells as a function of the age of the animal, and in old mice as many as 75 % of all liver cells may contain chromosomal aberrations microscopically visible when viewed at anaphase (Crowley & Curtis, 1963). Fur-thermore, ionizing radiation, which produces an effect in animals closely resembling prema-ture aging, also increases chromosomal aberra-tions, and the increase is proportional to the life shortening. More recently it has been shown that for two inbred strains of mice which live quite different life-spans but which die from a variety of degenerative diseases, the rate at which aberrations develop is roughly inversely proportional to the life expectancy (Crowley & Curtis, 1963). In addition it was shown that dogs, which age much more slowly than mice, also develop aberrations in their liver cells at a much slower rate than mice (Curtis, Leith, & Tilley, 1966). These results have greatly strengthened the mutation theory of aging (Curtis, 1963). It is well known that genetic factors play a very important part in determining life ex-pectancy. In man, the children of long-lived parents have a considerably greater than aver-age life expectancy. In animals, the genetic factors which determine life expectancy are more firmly established and understood than in humans (Gowan, 1962). In view of the relation between chromosomal stability and aging, it is then attractive to postulate that chromosomal stability is genetically controlled and that this forms an important part of the genetic component of longevity