Question

The Ras protein is a GTPase that functions in many growth-factor signaling pathways. In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bound, the signal is not transmitted. Mutations in the gene for Ras are found in many cancers. Of the choices below, which alteration of Ras activity is most likely to contribute to the uncontrolled growth of cancer cells?

Answer 1

Answer:

d) a change that decreases the rate of hydrolysis of GTP by Ras

Explanation:

• When bound to GDP, the Ras protein is inactive.
• When bound to GTP, the Ras protein is active and signals cell proliferation.

Ras is a GTPase; after being active for some time bound to GTP, it hydrolizes the GTP into GDP and becomes inactive once again.

If a mutation that caused a decrease in the rate of hydrolysis of GTP happened, Ras would be bound to GTP for longer periods of time, therefore active, therefore sending constant proliferation signals and increasing the risk of cancer due to uncontrolled cell division.