Fig. 4. Scp3 immunofluorescence staining of primary spermatocyte chromosomes from p53^+/- control (A,C,E) and Brca1^11/11p53^+/- mutant (B,D,F) mice. (A,B) Zygotene, (C,D) pachytene and (E,F) diplotene spermatocytes. Arrows in C,D indicate paired XY chromosomes. Arrows in E indicate chiasmata in diplotene spermatocytes of control mice. No normal diplotene chromosome spreads were found in mutant spermatocytes, although some cells show fragmented cores/SCs (F). (G) Comparison of pachytene and diplotene stage spermatocytes at P16 and P21. Two-thousand meiosis I spermatocytes were counted. Data are plotted as average percentage (mean±s.d.) determined from four pairs of mutant and control mice. There were no statistically significant differences in the numbers of pachytene stage spermatocytes between mutant and control mice (synapses; P0.08). A significant difference in the numbers of diplotene stage spermatocytes was observed (cross-over; P0.002).