How do genes control the differences in size and shape of the tubes?
Genetic variants exhibit striking differences in morphology that mimic natural shapes throughout the animal kingdom. Some variations affect patterning and alter the number of cells fated to produce the tubes; others affect morphogenesis and alter the cell biological processes that produce the tubes (Berg 2005). What are these genes and how similar are their roles in different developmental processes? How does a gradient of signaling information resolve into a sharp boundary between two distinct cell types? Several signaling pathways contribute to defining the two types of cells that make the dorsal appendage tubes. EGF and BMP signals are expressed in a graded fashion in the dorsal anterior follicle cells. These molecules induce Notch and Wingless signaling, which subdivide the primordium and establish a boundary between the two cell types (Ward and Berg 2005; Ward et al. 2006). How do these pathways refine the pattern within the epithelium? How do the two cell types coordinate their e
