Consider the Ras Signal-Transduction Pathway

Multiple Choice

Consider the Ras signal-transduction pathway. Suppose a mutation occurred in the gene that encodes MEK that renders it nonfunctional. Which of the following effects would you see in this situation?

A) Binding of the growth factor to the receptor would occur, but the receptor's conformational change that is needed for the pathway to go forward would not occur.
B) Activated Ras would no longer have the ability to activate Raf, and the signal-transduction pathway would be halted at this step.
C) Ras would lose the ability to bind GTP and thus could no longer become activated, and the signal-transduction pathway would be halted at this step.
D) MAP kinase would not be activated and thus could not move into the nucleus to activate transcription factors.
E) Inactive Ras would move into the nucleus and inactivate tumor-suppressor transcription factors, which could ultimately result in cancer.