Abstract: Cells regulate cell cycle progression by arresting several checkpoints in response to ionizing radiation,which provides time for them to repair DNA damage,ensures genomic integrity and genetic stability and in turn decreases genetic mutations.Different cells arrest different checkpoints such as G₁-,G₂- and S-phase checkpoint in response to different ionizing radiations,whereas G₂-phase arrest is more prevalent.More attention has been focused on Chk1,Chk2and p53in the study of mechanisms of ionizing-radiation-induced G₂ arrest these years.