Most sensitive structure in cell for radiotherapy is

(C) DNA # Radiotherapy is a physical form of treatment that damages any tissues in its path. Tumor cells seen somewhat more sensitive to the lethal effects of radiation than normal tissues primarily because of differences in ability to repair sublethal DNA & other damage.> In the target tissue,radiation damages DNA (usually single stand breaks) & generates free radicals form cell water that are capable of damaging cell membranes,proteins & organelles.> Since DNA is the most important subcellular target of ionizing radiation,rapidly dividing cells are more radiosensitive than quiescent cells. Radiation- damage is dependent on 02 ; hypoxic cells are more resistant. Cells in cell cycle of late G,& S are more reristant to radiation & cells in the G2 & M phases are most sensitive to Radiation