DNA extracts from camptothecin-treated HL-60 cells separated on an agarose gel and stained with SYBR® Green I nucleic acid gel stain (Cat. no. S7563, S7567, S7585). The 200 to 5000 bp DNA fragments characteristic of apoptotic cells (which appear as "ladders") are clearly visualized with this sensitive nucleic acid stain. Cell preparations were gifts of Zbigniew Darzynkiewicz, Cancer Research Institute, New York Medical College.