Question

Male cockroaches with mutations that strongly decrease the function of an RTK called RTKX are oblivious to the charms of their female comrades. This particular RTK binds to a small molecule secreted by sexually mature females. Most males carrying loss-of-function mutations in the gene for Ras protein are also unable to respond to females. You have just read a paper in which the authors describe how they have screened cockroaches that are mutant in RTKX for additional mutations that partly restore the ability of males to respond to females. These mutations decrease the function of a protein that the authors call Z. Which of the following types of protein could Z be? Explain your answer.

(a) a protein that activates the Ras protein by causing Ras to exchange GDP for GTP

(b) a protein that stimulates hydrolysis of GTP by the Ras protein

(c) an adaptor protein that mediates the binding of the RTKX to the Ras protein

(d) a transcriptional regulator required for the expression of the Ras gene

Answer 1

The protein Z could be a protein that activates the Ras protein by causing Ras to exchange GDP for GTP, which is important in the response to RTKs and the MAPK kinase cascade. Mutations in the Ras protein that prevent GTP hydrolysis are associated with cancer.

Step-by-step explanation:

Z, the protein described in the paper that restores the ability of male cockroaches to respond to females, could be (a) a protein that activates the Ras protein by causing Ras to exchange GDP for GTP.

Ras is a G-protein connected with the response to RTKs and it initiates the MAPK kinase cascade when GDP is released and GTP is uploaded.

Mutations in the Ras protein that interfere with its GTPase activity are common in cancer, which can lead to uncontrolled cell proliferation.