[en] Organisms have the ability to protect their genetic materials against endogenous and environmental agents such as reactive oxygen species (ROS), ionizing radiation and a variety of chemical compounds. The basis of the protection mechanisms has been evolutionarily conserved, from yeast to human, but each organism has often specialized mode of regulation by using different set of machineries, especially in lower eukaryotes. In this review, we describe novel findings about the unconventional molecular mechanisms of DNA repair, DNA damage response, and genetic and phenotypic variations involved in adaptation to environmental conditions, in the budding yeast Saccharomyces cerevisiae. These findings provide insights on how organisms adapt to the environmental stresses to survive to the next generation through the evolutionary process. (author)