In a hypothetical embryo, a high concentration of a morphogen called morpho is needed to activate gene P; gene Q is active at or above medium concentrations of morpho; and gene R is expressed so long as any quantity of morpho is present. A different morphogen, called phogen, activates gene S and inactivates gene Q when at medium to high concentrations. If morpho is produced in the anterior end of the embryo and phogen is produced in the posterior end of this embryo, which genes will be expressed in the middle region of the embryo