Cell cycle defects of E2f4^–/– fetal liver erythroid cells in vivo. (A) Cell cycle profile of live Ter119⁺ gated E15.5 FL cells stained with DNA dye, DRAQ5. Percentage of cells in each cell cycle stage was determined by Modfit (*proportion of cells in G₂/M, as determined by Modfit, may include cells in late S phase). (B) FACS determination of BrdU incorporation by Ter119⁺ E15.5 FL cells following 1 hour in vivo BrdU pulse. For quantitation, see Table 1. (C) Phosphohistone H3 and MPM2 staining was performed on whole E15.5 FL cells to determine proportion of cells undergoing mitosis. Numeric data are provided with the corresponding standard deviation.