Analyzes the manner in which a small G protein Cdc42 functions to polarize budding yeast. Polarization of Cdc42 in the absence of upstream cues or positive feedback from the cytoskeleton; Requirement of the scaffold protein Bem1 and cycling of Cdc42 between its GTP- and GDP-bound states for polarization; Importance of G proteins for mediating signals to direct cell polarization and macro molecular assembly in all eukaryotes.