Question

32. Study the signaling pathway illustrated below, which involves two different receptors. Assume that a protein is active only when it is activated, but not inhibited, by its upstream signaling molecules. Activation and inhibition are indicated by normal and blunt arrows, respectively. Assume that the transcription regulator can be activated by either the binding protein or the kinase that are immediately upstream of the transcription factor. Under which of the following conditions will the expression of target:gene "X" be induced? Signal 1 Signal 2 GPCR RTK G protein Kinase 0-0 Enzyme Kinase Adaptor Second messenger Binding protein Kinase -- Transcription regulator + Gene "X" expression and cellular response A: Only in the presence of both signals B: In the presence of either or both signals C: In the presence of either signal but not both of them D: Only in the absence of both signals E: Only in the presence of sienal 2 but not signal 1

Answer 1

32 (C) is the correct answer .

As we see in the functioning pathway of both the the receptor GPCR and RTK , there intermediate inhibit others , so both the receptor can't present on the the same membrane.

From pathway , the Rafkinase inhibit enzyme Adenyl cyclase , Adenyl cyclase(AC) worked on ATP and convert it in secondary messanger . If both pathway worked together AC get inactivated and further parthways are blocked.

Similarly G protein with the help of adaptor molecule , inhibit transcription protein , so no transcription is held , so no new protein is formed. There for we say that only the presence of either not both of them we found the following target gene X.

Target gene X can be produced by both of the receptor GPCR and RTK , but at a time only one is working .