posted by M.C.Filth .
Select two signal mechanisms that activate transcription in response to an external signal. Any of these systems ultimately activates a transcription factor. For each of the systems you have selected, trace the route from signal binding to receptor to the final transcription factor activation. For each of the systems you have chosen, indicate one mutation that would result in failure to respond to the signal (here, we will assume that signal-receptor binding is intact because that possibility is just too easy) and one mutation that would result in constitutive activation of transcription.