A proposal that carcinogens of many sorts act by inducing the expression of retrovirus genes already resident in the target cell. It is now known that while cells from different species harbor genes homologous to retrovirus oncogenes, the cellular genes were the progenitors of the viral oncogenes. The cellular genes are now called proto-oncogenes (q.v.) and they evidently function in the normal physiology of cells from evolutionarily diverse species. See Chronology, 1969, Huebner and Todaro.
Subjects: Genetics and Genomics.