DNA damage by ionizing radiation

DNA damage by ionizing radiation refers to the molecular and cellular effects caused when high-energy radiation interacts with DNA molecules. Ionizing radiation includes X-rays, gamma rays, alpha and beta particles, and neutrons. It is capable of releasing electrons from atoms or molecules (ionization), which can break covalent bonds in biological macromolecules such as DNA. Types of damage include single-strand breaks (SSBs), double-strand breaks (DSBs), base damage, apurinic/apyrimidinic (AP) sites, DNA–protein crosslinks (DPCs), and clustered/complex lesions. If not properly repaired, these damages can result in cell death, mutagenesis leading to cancer development, or genomic instability. A key signature distinguishing ionizing-radiation-induced damage from endogenous chemical agents is damage clustering. Additionally, indirect effects via ROS generation contribute secondarily by producing diffusible damaging species affecting nearby genetic material.