Question

Ras is a GTP-binding protein involved in cell proliferation (division). In its active form, with GTP bound, Ras activates cell signaling pathways that promote cell division. Mutations in the gene that encodes Ras can lead to cancer. How might mutations in the gene encoding Ras lead to the uncontrolled proliferation characteristic of cancer cells?
A. They prevent Ras from being made.
B. They increase the rate at which Ras hydrolyzes GTP.
C. They decrease the protein’s affinity for GTP.
D. They increase the protein’s affinity for GDP.
E. They decrease the rate at which Ras hydrolyzes GTP.

Answer 1

Answer:

E. They decrease the rate at which Ras hydrolyzes GTP.

Explanation:

Activated Ras has GTP bound to it, this propagates an intracellular signal to the nucleus where cell proliferation is induced. Thereafter proliferation is switched off by the hydrolysis of the bound GTP to GDP.

Therefore decreasing the rate of GTP hydrolysis causes Ras to remain active, ultimately leading to uncontrollable proliferation characteristic of cancer.