a. Would you expect a cell to continue or stop dividing at a nonpermissive high temperature if you had isolated a temperature-sensitive RAS mutant that remained fixed in the GTP-bound form at nonpermissive temperature? b. What would you expect if you had a temperature sensitive mutant in which RAS stayed in the GDPbound form at high temperature?
RAS when bound to GTP is active. Active RAS-GTP inturn activates a series of three protein kinases called MAPkinase cascade.These activated kinases inturn activate transcription factors which transcribe genes of proteins required for cell cycle and therefore lead to cell proliferation.
Hence, in such a case where RAS remains bound to GTP at non- permissive temperature, the cell would keep dividing as the activated RAS would keep signalling the cell to divide, at non permissive high temperature.