Cell cycle control genes, the products of which are essential for cell division. Many are known and they are highly conserved, with human genes able to restore function to yeast cells in which the homologue is mutated. The product of the cdc42 gene is a rho GTPase family member (191 aa) involved in control of cell morphology, migration, endocytosis, and cell cycle progression. It induces the formation of filopodia by activating the Arp2/3 complex thereby affecting the actin cytoskeleton. The product of oncogene dbl stimulates the dissociation of GDP from cdc42, allowing activation to occur when GTP binds. See cyclins; DREAM complex.