1. During development groups of inducing cells called organizing centers secrete graded growth factor signals. The concentration gradient of a"morphogen"can induce multiple cell differentiation choices inductive signal OOOOO ○○○o○o●●○o○○○ cells directed to new developmental pathway Figure 21-12. Molecular Biology of the Cell, 4th Edition.1. During development groups of inducing cells called organizing centers secrete graded growth factor signals. The concentration gradient of a “morphogen” can induce multiple cell differentiation choices. Fig. 1