Fig. 1. The topi meiotic arrest phenotype. (A) Phase-contrast image of wild-type whole testis, apical tip in top right-hand corner. Primary spermatocytes occupy most of the apical end (arrows) Elongating spermatid bundles (arrowheads) are seen inside the testis, and spilling out from the distal end. (B) Phase-contrast image of topi^Z3-2139 whole testis. Only stages up to mature primary spermatocytes (arrows) are seen. Degenerating primary spermatocytes are present in the distal region of the testis (arrowheads). (C-H) High-magnification views of mature spermatocytes from squashed preparations of wild-type (C-E) and topi^Z3-2139 (F-H) testes viewed by phase-contrast (C,F) and Hoechst DNA staining (D,G) or both visualization methods simultaneously (E,H).