Fig. 2. The 3' eye enhancer is dispensable for dac activation in vivo. (A) dac⁷ is associated with a deletion, beginning at exon 9, that uncovers the entire 3' genomic region of dac. (B-D) Scanning electron micrographs (SEMs) of adult eyes from wild-type (B), dac⁷ (C) and dac³ (D) animals. (E-G) Third instar eye imaginal discs from wild type (E), dac⁷ (F) and dac³ (G) animals stained with a monoclonal Dac antibody, mab2-3. dac⁷ eye discs show relatively normal Dac protein expression when compared with wild-type eye discs (compare F with E). dac⁷ adult eyes are rough and disorganized but still contain 50% of the normal number of ommatidia (compare C with B). By comparison, dac³ homozygotes express no Dac protein (G) and develop with no eyes (D). (H,I) A first instar (H) and second instar (I) eye disc of wild type shown for comparison with J and L. (J-M) Late first (J) and third (K) instar eye imaginal discs from 5EE-lacZ and second (L) and third (M) instar eye imaginal discs from 3EE-lacZ transgenic larvae. ß-Galactosidase activity is detected in both first instar and third instar 5EE-lacZ eye discs, primarily at the posterior margin (J,K). The earliest 3EE-lacZ reporter expression is observed in second instar eye discs and this ß-galactosidase activity persists in the third instar eye disc (L,M).