You create double mutant cells with the permanently active PK1 and an inactivated PK2. You find the cells still respond even when no signal is present. In the normal kinase cascade, does PK1 activate PK2 or does PK2 activate PK1

Kinase cascade

Explanation:

Normally, PK2 activates PK1

PK1 and PK2 normally work sequentially in an intracellular signaling pathway If PK1 is permanently activated, a response is seen independently of whether or not PK2 is present If PK1 activated PK2, no response should be seen if PK1 were activated in the absence of PK2 PK2 normally needs to activate PK1 for the cells to respond to the signal When PK2 is permanently activated in the absence of PK1, PK1 is not there to relay the signal