Induction of apoptosis in WEHI 3b leukemic cells by cytochrome c. Cells were analyzed by flow cytometry 2 hours (a and b) and 4 hours (c and d) after electroporation with bovine cytochrome c. The percentages of apoptotic fraction (gate A) were as follows: (a) control (6%); (b) with cytochrome c (12%); (c) control (8%); with cytochrome c (28%). Note the progressive increase in apoptotic fraction and loss in G2/M with cytochrome c.