The fraction of cells with residual RAD51 foci is correlated with the fraction of cells that die. Panel a: SiHa cells were exposed to X-rays and allowed to recover for 24 hours. Cells were fixed and co-immunostained for γH2AX and RAD51, and cells with foci were scored. Results are the means and SD for 3 experiments. Panel b: The fraction of SiHa cells lacking RAD51 foci is compared with the clonogenic fraction measured 24 hours after exposure to X-rays. Panel c: Several cell lines were exposed to 2 Gy, allowed to recover for 24 hours, and then examined for the fraction of cells that lacked RAD51 foci. Panel d: RAD51 (green) and γH2AX (red) antibody staining of SiHa cells 24 hours after exposure to 2 Gy. Nuclei are stained blue with DAPI. Panel e: 24 hours after exposure to 8 Gy. Note the micronuclei stained with antibodies to RAD51 and/or γH2AX foci and the co-localization of some foci in some cells but not all cells.