Imagine that two protein kinases, pk1 and pk2, act sequentially in an intracellular signaling pathway. when either kinase is completely inactivated, the cells don’t respond to the signal. doubly mutant cells that contain inactivated pk2 and permanently active pk1 respond in the absence of a signal. in the normal signaling pathway, does pk1 activate pk2 or does pk2 activate pk1? what outcome would you have predicted for a doubly mutant cell line with an activating mutation in pk2 and an inactivating mutation in pk1?

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Explanation:

We know for sure that PK2 activates PK1 in a significantly signaling pathway. This is mainly because PK1 is permanently activated as a independent response which is observed in the status of PK2, by indicating that PK2 is fully activated downstream of PK1.

In the case that based on observation and experience, a setup were modified in a such a way PK1 was mutationally inactive and PK2 carried an activating mutation, we would not find any response observed since PK2 would not be able to activate PK1. The most importantly is that the logic is whether you discuss that PK1 activated PK2, I  responded to this question part mainly based on this sequence.

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