Figure 3.

Two fundamental roles of morphogen gradients in development. It is well known that morphogen gradients provide quantitative information to coordinate proliferation with differentiation. For instance, morphogen gradients induce the production of different cell fates (A, B, C, D) according to thresh hold concentrations of the morphogen. Morphogen gradients may also integrate directional information by controlling planar cell polarity indicated by uniform asymmetrical localization of key polarity protein (shown in blue) and cellular behavior like the uniform orientation of cell extensions like cilia (yellow).