General physiology: JAK-STAT signalling: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · General physiology: JAK-STAT signalling

Sample item

Growth hormone receptors have no intrinsic enzyme activity. After the hormone binds, which mechanism transmits the signal into the cell?

AAssociated JAK kinases that phosphorylate STAT proteinsBGs activation and cAMP-dependent protein kinaseCAn intrinsic tyrosine kinase domain, as in the insulin receptorDDirect binding of the hormone-receptor complex to DNA

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Associated JAK kinases that phosphorylate STAT proteins

Cytokine-class receptors such as those for growth hormone and prolactin signal through receptor-associated Janus kinases. The JAKs phosphorylate STAT proteins, which dimerise and move to the nucleus to alter transcription.

Option by option

A. Associated JAK kinases that phosphorylate STAT proteins (correct)
Correct. JAK phosphorylation of STAT is the signalling route of these receptors.
B. Gs activation and cAMP-dependent protein kinase
Growth hormone does not signal chiefly through Gs and cAMP.
C. An intrinsic tyrosine kinase domain, as in the insulin receptor
An intrinsic tyrosine kinase is a feature of the insulin and growth-factor receptors, not of the growth hormone receptor.
D. Direct binding of the hormone-receptor complex to DNA
Direct DNA binding is the pattern of intracellular steroid and thyroid hormone receptors.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Associated JAK kinases that phosphorylate STAT proteins. Cytokine-class receptors such as those for growth hormone and prolactin signal through receptor-associated Janus kinases.

Why is "Gs activation and cAMP-dependent protein kinase" not the answer?

Growth hormone does not signal chiefly through Gs and cAMP.

Why is "An intrinsic tyrosine kinase domain, as in the insulin receptor" not the answer?

An intrinsic tyrosine kinase is a feature of the insulin and growth-factor receptors, not of the growth hormone receptor.

Why is "Direct binding of the hormone-receptor complex to DNA" not the answer?

Direct DNA binding is the pattern of intracellular steroid and thyroid hormone receptors.

What concept does this question test?

It tests General physiology: JAK-STAT signalling in Physiology. The JAKs phosphorylate STAT proteins, which dimerise and move to the nucleus to alter transcription.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study General physiology: JAK-STAT signalling?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.