Fig. 1. PCP is evident in the coordinate organization of wing hairs and eye ommatidial clusters in the fly. Mutations in PCP genes cause cells to lose their planar organization, yet maintaining their individual cell polarity. Loss of PCP genes in the wing can cause misorientation of hairs, or multiple hairs to form in a single cell. Loss of PCP genes in the eye can cause alterations in degree of rotation, dorsal-ventral inversions, and loss of the chiral, asymmetric organization of the ommatidia. Cells appear to have lost their `compass' yet maintain their identity.