Fig. 1. Mosaic analysis with Dl. (A) Eye imaginal disc (anterior towards the left). Dl protein (magenta) accumulates in the differentiating region posterior to the morphogenetic furrow (arrowhead). Mitotic cells (labeling for phosphorylated histone H3 in green) are absent from the morphogenetic furrow region where the cell cycle is arrested. R8 cells are always specified from cells born anterior to the morphogenetic furrow when Dl protein is undetectable. (B) Phase-contrast micrograph of an eye section through the apical R7 level. Photoreceptor cells homozygous mutant for Dl are detected by absence of dark pigment granules at the rhabdomere base. Two ommatidia in this section lack any Dl mutant photoreceptor cells (green stars). All the other ommatidia contain one or more mutant cells. A variety of developmental defects are seen in these ommatidia. (C) Bright-field micrograph through the same eye at the basal R8 level. Every R8 cell is pigmented and therefore wild type for Dl (arrows).

Return to article