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Discussion: Blue stain was observed in the wing and leg imaginal discs of En-lacZ larva. Therefore, it was suggested that the promoter lacZ was successfully incorporated into the Drosophila genome. The posteriorly localized staining patterns observed in the En-lacZ larva wing and leg discs match significantly with the known engrailed expression patterns (Gilbert, 2003). However, result of the experiment is not sufficient to conclude that engrailed is expressed in the posterior regions of all imaginal discs. Other types of En-lacZ lava's imaginal discs must also be observed before coming to that conclusion. Simply observing the expression patterns of engrailed is not helpful in determining the exact roles of engrailed. The literature notes that engrailed might be involved in the compartmentalization and anterior-posterior patterning of the imaginal discs (Gilbert, 2003). Verification of such roles of engrailed requires further experimentation involving engrailed double mutants. If the double mutants were to exhibit imaginal disc deformities involving compartmentalization or anterior-posterior pattering, then the function of engrailed would be revealed. However, it is noteworthy that engrailed carries out its roles through complex interactions with other genes, such as hedgehog, dpp, and omb. Therefore, connecting deformities observed in the double mutants to the exact roles of engrailed is cursory at best; deformities observed could either be primary or secondary effects caused by the deletion of engrailed which could be acting as either an inhibitor or an activator. Another observation made in the experiment was the phenotypic difference between the leg imaginal discs of the wildtype larva (Figure 3A)and En-lacZ larva (Figure 3B). Each of the three sets of adult Drosophila legs is phenotypically different (Cruz, 1993), therefore it was suggested that each of the leg imaginal discs should also be different in appearance. It was also suggested that there are three phenotypically different pairs of leg imaginal discs, each corresponding to the fore, mid, and hind legs. In fact, the difference is noticeable in the results (Figure 3). In the leg imaginal disc of the wildtype larva (Figure 3A), there is a greater number of internal concentric compartments than in the En-lacZ larva's leg imaginal disc (Figure 3B). Consulting Cruz (1993)(Figure 1), it was suggested that the wildtype larva's leg imaginal disc dissected out in the experiment corresponds to the mid-leg of the adult fly. On the other hand, the leg imaginal disc of En-lacZ larva has fewer numbers of internal concentric compartments than wildtype larva's and has a dark crescent in the center. Also, it is blunter on its dorsal end (Figure 3B). Consulting Cruz (1993)(Figure 1), it was conjectured that the En-lacZ larva's leg imaginal disc corresponds to the adult fore-leg. Different types of leg imaginal discs were retrieved ultimately because only one leg imaginal disc was randomly dissected out from each strain of larva. In a future experiment, same type of leg imaginal discs should be dissected out of wildtype and En-lacZ larvae for better contrast in ß-galatosidase reporter activity. Moreover, all three types of leg imaginal discs should be dissected out to confirm that there are, in fact, observable phenotypic differences among the leg imaginal disc pairs.
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