G-PAP) G-PIP H-Hormone R Membrane receptor G G protein ? G-PAP G-protein activat
ID: 270071 • Letter: G
Question
G-PAP) G-PIP H-Hormone R Membrane receptor G G protein ? G-PAP G-protein activating protein G-PIP G-protein inactivating proteirn PP- Phosphorylating protein TAP TAP-Transcription activation protein Cell Division 53. The diagram above represents a model of signal transduction pathways ( and I) in a cell that is targeted by two ays are identified in the figure an inactive or active form. When the components a different hormones (H, and Hy). The components of the signal transduction pathw legend. Each cellular molecule in both pathways can exist in in pathway I are sequentially activated, the TAP molecules promote cell division. When the components in pathway II are sequentially activated, downstream signaling by the G protein is inbibited. Based on the model, which of the following mutations is most likely to result in a cell that will generate a cancerous tumor? (A) A mutation in the gene encoding PP that results in a nonfunctional protein (B) A mutation in the gene encoding G-PIP that results in a nonfunctional protein (C) A mutation in the gene encoding R, so that it is inactive even in the presence of H (D) A mutation in the gene encoding R, so that it is active even in the absence of HExplanation / Answer
Answer: Choice B
Reason: According to the illustration, two separate pathways, each antagonist of the other, are being carried out. Whereas the pathway I is promoting cellular signalling, pathway II is preventing cellular signalling. Thus, any mutation which causes de-activation of the pathway II or over-activation of pathway I will lead to uncontrolled cell proliferation.
When the G-PIP would be non-functional in nature, it will not prevent blocking of the signalling pathway at the point 'G' and hence, the normal down-stream signalling cascade leading to active cell proliferation will continue leading to cancerous cell division.
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