Canadian Nuclear Laboratories 1 article published in JoVE Biology Measuring DNA Damage and Repair in Mouse Splenocytes After Chronic In Vivo Exposure to Very Low Doses of Beta- and Gamma-Radiation Matthew Flegal1, Melinda S. Blimkie1, Heather Wyatt1, Michelle Bugden1, Joel Surette1, Dmitry Klokov1 1Radiological Protection Research and Instrumentation, Canadian Nuclear Laboratories A protocol to evaluate changes in DNA damage levels and DNA repair capacity that may be induced by chronic in vivo low dose irradiation in mouse spleen lymphocytes, by measuring phosphorylated histone H2AX, a marker of DNA double-strand breaks, using flow cytometry is presented.