Figure 2: Centrosome theoretical geometrical model: functioning. Small ellipses represent γ-TuRCs on the centrosome (large sphere): each one is identified by its own private receptor specific for its longitude and latitude(capital letters: A, B, C) which recognizes only the corresponding targeting sequence. Each γ-TuRC has the orientation of the plane which, in that point, is tangent to the centrosome “spherical” surface. MTs (arrows) are nucleated with directions imposed by the orientation of the corresponding γ-TuRC: like orientation, like direction (one “discrete” orientation, one “discrete” direction). So, a molecular complex (twisted tube) through its “geometric” targeting sequence, recognizes and links exclusively the receptor (A or B or C) that marks that γ-TuRC which has the correct orientation to nucleate a microtubule directed to the desired (corresponding: A or B, or C) destination, reached through a kinesin carrier (wheel): one targeting sequence, one γ-TuRC receptor, one cortical compartment: one-to-one univocal correspondence. (From: M. Regolini Centrosome: a geometrical model Lambert Academic Publishing Germany 2014)