A variety of DNA damage is introduced on our genome due to the action of genetic toxins. DNA damage causes mutations and chromosomal aberrations, which cause cancer and aging. To maintain genome integrity, various DNA repairs are provided in all organisms. In case genes responsible for DNA repair are muted, these individuals show metabolic disorders and premature aging. Furthermore, accumulation of mutations increases the risk of developing cancer. In this laboratory, we would like to elucidate the mechanism of how toxic substances in the environment act on organisms and the survival strategy of living organisms against it, with emphasis in understanding roles of DNA repairs.