Detection of apoptosis-associated DNA strand-breaks by in situ TdT assay in WSU-CLL cells. The cells were either untreated (CTRL) or exposed to melarsoprol for 24 and 48 hours, respectively. The dots represent the distribution of individual cells with respect to their b-dUTP incorporation and DNA content. The degree of b-dUTP complexes correlated with DNA strand-breaks per cell.