(B) Active BAX (6A7) and active caspase‐3 were also quantified by staining the cortex of 1‐ to 14‐day‐old MCL‐1Δ/Δ mice. Representative images from at least three sections from each animal were counted. The total number of cells was determined by counting the Hoechst‐positive nuclei. Data are expressed as percent of positive cells for at least three animals per genotype±s.d. *P0.05. 