RPA1 and Alzheimer disease: At 4 h after irradiation most YD cells in G1 were still devoid of RPA foci, but the frequency of RPA-positive cells (≥ 5 foci) in AD cells had increased significantly (0% in YDs vs. ≥ 10% in ADs; Fisher’s exact test; p-value < .05) (Figure 4F, 4G).