Chromatin staining of Drosophila testes

This protocol describes chromatin staining of Drosophila testes. To visualize DNA, preparations fixed using methanol-acetone, paraformaldehyde, or formaldehyde can be stained with several DNA-binding dyes. If the slides are to be examined with a fluorescence microscope equipped with filters that permit ultraviolet (UV) excitation, suitable dyes for DNA staining are Hoechst 33258 or 4',6-diamidino-2-phenylindole (DAPI). If the slides are to be analyzed with a confocal microscope not equipped with a UV laser, DNA can be stained with either propidium iodide or TOTO-3 iodide.