I prefer egg laying bottles because the parameters for irradiation are more consistent. Collect embryos for 12 hours at 25 C. Repeat collection. If you want to generate larger clones, irradiate at an earlier time, but be prepared to generate clones at a lower frequency. If using egg-laying plates, cut the plates in halves or quarters and place each piece in a bottle. When the flies have eclosed, they can be screened for clones.
Most white clones appear black under a dissecting microscope.
Fix and section the eyes as described in Section 19. However, before the flies are sacrificed, shine a bright light on them for a few minutes. This causes the pigment granules in the photoreceptor cells to migrate apically and makes it easier to score for white pigment in cells R7 and R8. Cut 1 to 4 micron thick sections and collect all of the sections serially. This is important as pigment may only be visible in R7 and R8 cells for one or a few sections.