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2. An intracellular signaling pathway makes molecule Z. The first protein involv

ID: 133679 • Letter: 2

Question

2. An intracellular signaling pathway makes molecule Z. The first protein involved in this athway is a receptor protein called X. Once X is activated, it is unclear whether protein R or Y act next in this pathway to the produce Z. To order this signaling pathway various experiments are performed (like the ones we talked about in class). In experiment I, when R is mutated to be constitutively active and Y is mutated to be nonfunctional, Z is made. However, in experiment II, when R is mutated to be nonfunctional and Y is constitutively active, Z is not made. Circle the correct order of this intracellular signaling pathway to make Z7(3 pts)

Explanation / Answer

2.

From the question it is clear that the first protein (X) is a receptor protein.

From the experiment I, mutated R is constitutively active and mutated Y is non functional but the Z is produced. As mutated R is constitutively active so it does not require any signal to produce Z.

From the experiment II, mutated R is non functional and mutated Y is constitutively active but Z is not produced. So, we can say that, for production of Z the signal from R is required.

After comparing both of the experiments, we can say the previous gene of Z is R. So, the correct order of this intracellular signalling pathway is X -> Y -> R -> Z.