Blood and immunity: nuclear-cytoplasmic dissociation: 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 · Blood and immunity: nuclear-cytoplasmic dissociation

Sample item

A marrow film shows large erythroid precursors with open, immature nuclear chromatin although the cytoplasm is well haemoglobinised. Which biochemical lesion explains this nuclear-cytoplasmic asynchrony?

AImpaired thymidylate and DNA synthesis, with RNA and protein synthesis intactBReduced globin chain output from gene deletionCExcess erythropoietin driving early release of immature cellsDDefective haem synthesis with preserved DNA synthesis

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

The answer and the reasoning

A. Impaired thymidylate and DNA synthesis, with RNA and protein synthesis intact

In vitamin B12 or folate deficiency, thymidylate synthesis fails, so DNA replication and nuclear maturation lag. RNA and haemoglobin synthesis continue, so the cytoplasm matures normally and the nucleus looks immature, giving megaloblasts and macrocytes.

Option by option

A. Impaired thymidylate and DNA synthesis, with RNA and protein synthesis intact (correct)
Correct. DNA synthesis lags while cytoplasmic maturation proceeds.
B. Reduced globin chain output from gene deletion
Reduced globin output also gives small hypochromic cells, as in thalassaemia.
C. Excess erythropoietin driving early release of immature cells
Erythropoietin excess shortens maturation and does not delay nuclear development.
D. Defective haem synthesis with preserved DNA synthesis
Defective haem synthesis gives small, poorly haemoglobinised cells.

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, Impaired thymidylate and DNA synthesis, with RNA and protein synthesis intact. In vitamin B12 or folate deficiency, thymidylate synthesis fails, so DNA replication and nuclear maturation lag.

Why is "Reduced globin chain output from gene deletion" not the answer?

Reduced globin output also gives small hypochromic cells, as in thalassaemia.

Why is "Excess erythropoietin driving early release of immature cells" not the answer?

Erythropoietin excess shortens maturation and does not delay nuclear development.

Why is "Defective haem synthesis with preserved DNA synthesis" not the answer?

Defective haem synthesis gives small, poorly haemoglobinised cells.

What concept does this question test?

It tests Blood and immunity: nuclear-cytoplasmic dissociation in Physiology. RNA and haemoglobin synthesis continue, so the cytoplasm matures normally and the nucleus looks immature, giving megaloblasts and macrocytes.

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 Blood and immunity: nuclear-cytoplasmic dissociation?

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.