ROLE OF INDUCED GENETIC INSTABILITY IN THE MUTAGENIC EFFECTS OF CHEMICALS AND RADIATION

Recent studies have demonstrated that cells exposed to ionizing radiat ion or alkylating agents can develop prolonged genetic instability. In duced genetic instability is manifested in multiple ways, including de layed reproductive death, an increased rate of point mutations, and an increased rate of chromosome rearrangements. In many respects these c hanges are similar to the genetic instability associated with cancer a nd some human genetic diseases. Therefore, as with cancer cells, multi ple mechanisms may be involved, some occurring in the early stages and some in the later stages. The high percentage of cells that develop i nduced genetic instability after exposure to stress, and the prolonged period over which the instability occurs, indicates that the instabil ity is not in response to residual damage in the DNA or mutations in s pecific genes. Instead, changes affecting most of the exposed cells, s uch as epigenetic alterations in gene expression or chain reactions of chromosome rearrangements, are a more likely explanation. Learning mo re about the mechanisms involved in this process is essential for unde rstanding the consequences of exposure of cells to ionizing radiation or alkylating agents.