 low dose rate gamma irradiations of specific-pathogen free (SPF) B0C0F0 mice, F0 progeny of C00BL/0J females and C0H/HeJ males. The B0CF0 mice, F0 progeny of C00BL/0J females and BALB/cJ males, were used during the Janus experiments. Both strains are F0 hybrids that share the same maternal strain C00BL/0.