Molecular biology and genetics: cytogenetic methods: practice question

A Biochemistry 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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Biochemistry · Molecular biology and genetics: cytogenetic methods

Sample item

A bone marrow sample from a patient with suspected chronic myeloid leukaemia yields too few dividing cells for karyotyping. Which technique can still detect the BCR-ABL fusion?

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

The answer and the reasoning

D. Interphase fluorescence in situ hybridisation

FISH with probes for BCR and ABL can detect the fusion in non-dividing interphase nuclei. Karyotyping needs metaphase cells. Reverse-transcription PCR is also used for detection.

Option by option

  • A. G-banding of metaphase chromosomes

    G-banding needs metaphase chromosomes.

  • B. Western blotting for the fusion protein

    Western blotting would be indirect and is not a routine diagnostic.

  • C. Flow cytometry for CD34 expression

    Flow cytometry for CD34 counts blast cells and does not identify the BCR-ABL fusion.

  • D. Interphase fluorescence in situ hybridisation (correct)

    Correct. Interphase FISH does not need dividing 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.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Interphase fluorescence in situ hybridisation. FISH with probes for BCR and ABL can detect the fusion in non-dividing interphase nuclei.

Why is "G-banding of metaphase chromosomes" not the answer?

G-banding needs metaphase chromosomes.

Why is "Western blotting for the fusion protein" not the answer?

Western blotting would be indirect and is not a routine diagnostic.

Why is "Flow cytometry for CD34 expression" not the answer?

Flow cytometry for CD34 counts blast cells and does not identify the BCR-ABL fusion.

What concept does this question test?

It tests Molecular biology and genetics: cytogenetic methods in Biochemistry. Karyotyping needs metaphase cells. Reverse-transcription PCR is also used for detection.

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 Molecular biology and genetics: cytogenetic methods?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.