Flow cytometry analysis of BrdU incorporation in actively cycling Ramos cells. For in vitro labeling of cells, 20 µL of a 1 mM BrdU/PBS solution was added to 2 mL cell suspension containing 2x10^6 Ramos cells and incubated for 2 hours at 37C. Formaldehyde fixed cells were washed and permeabilized. To expose DNA incorporated BrdU, cells were treated with DNase for 1 hour at 37C. Actively cycling Ramos cells were stained with a BrdU-DyLight 488 conjugated monoclonal antibody (Product # MA3-071-D488, red histogram) at a 1:100 dilution for 30 min at room temperature. Unstained cells (black histogram) and unlabeled cells (blue histogram) were used as negative controls. A representative 10,000 cells were acquired for each sample.