(A), (B), and (C) show ventral views of hs-stg embryos that were fixed and stained with anti-cyclin A antibodies 0, 5, and 15 min after a 25 min heat pulse (37°C), initiated at 175 min AED. Cyclin degradation, which occurs at metaphase, occurs in a stochastic pattern that encompasses virtually all of the embryonic cells within 15 min of the heat pulse. See Figures 2A, 2B, and 2C for normal cyclin A expression patterns during cycle 14. (D) shows anaphase chromosomes in a hs-stg–induced mitosis. Note the absence of abnormalities such as chromosome bridges.