The order of events in a signaling pathway can be determined by the analysis of mutants.Cells that express a mutant defective Raf protein cannot be stimulated to proliferate uncontrollably by constitutively active Rasᴰ (dominant active).This indicates:
A)quiescent cells can be induced to proliferate in the absence of growth factors if they contain a constitutively inactive mutant Raf protein.
B)Raf is upstream of Ras in the signaling pathway.
C)Ras is upstream of Raf in the signaling pathway.
D)Ras mutants are recessive to Raf mutants.

Question

Quizplus · Accepted Answer

Ras being upstream of Raf in the signaling pathway is indicated by the fact that cells with a defective Raf cannot be stimulated by an active Ras to proliferate uncontrollably. This suggests that Ras's activity is dependent on Raf functioning properly downstream in the pathway for the signal to continue, leading to cell proliferation.

The Order of Events in a Signaling Pathway Can Be