Genetic ablation of caspases leads to increased aneuploidy in mitotic cells from the embryonic mouse cortex. A, Analysis of metaphase chromosome counts showed increased aneuploidy in E14 caspase-3 and caspase-9-null cortices compared with wild-type cortices from littermates (100 metaphase spreads were counted per embryo; for caspase-3, n = 3; *p = 0.02; for caspase-9, n = 3; *p = 0.04, Student's t test). B, Quantitation of DNA content by flow cytometry showed a significant 3–4% decrease in overall DNA content from cortices of E14 caspase nulls compared with sex-matched, wild-type littermates (caspase-3 wild-type and nulls, n = 4, *p = 0.002, Student's t test; caspase-9 wild-type and nulls, n = 3, *p = 0.03, Student's t test). C, Histogram of the distribution of aneuploidy in E14 wild-type (black), caspase-3-null (red), and caspase-9-null (blue) NPCs. Caspase-deficient cells showed expanded distribution of numerical aneuploidies.