20. The signaling pathways shown below integrate information provided by signal 1 and signal 2 to activate the transcription of a target gene and trigger a cell response. The intracellular signaling molecules in the pathway are only active when they receive an activating signal () from an upstream signaling molecule and are not being inhibited (-l) by any upstream signaling molecule. activated GPCR activated RTK G protein kinase phosphatase enzyme kinase second messenger -binding protein kinase transcription regulator gene expression and cellular response Given this information, under what conditions will the target gene for this signaling network be expressed? a. The target gene will be expressed only when signal 1 is present. The target gene will be expressed only when both signals are present. C. The target gene will-be expressed only when signal 2 is present. d. The target gene will be expressed only when both signals are absent. e. The target gene will be expressed when either signal is present on its own