Molecular biology and genetics: cDNA cloning: 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: cDNA cloning

Sample item

A researcher wants bacteria to produce a human protein, but bacteria cannot splice introns. Which DNA should be cloned into the expression vector?

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

The answer and the reasoning

B. DNA copied from mature mRNA by reverse transcriptase

Complementary DNA is made from processed mRNA with reverse transcriptase, so it lacks introns and can be expressed in bacteria. Genomic DNA would retain introns that bacteria cannot remove. A promoter alone contains no coding sequence.

Option by option

  • A. A genomic fragment containing the introns

    Introns in genomic DNA would not be spliced out in bacteria.

  • B. DNA copied from mature mRNA by reverse transcriptase (correct)

    Correct. cDNA from mature mRNA contains only exons.

  • C. The promoter region alone

    A promoter does not encode the protein.

  • D. Satellite DNA from the centromere

    Satellite DNA is non-coding repetitive sequence.

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 B, DNA copied from mature mRNA by reverse transcriptase. Complementary DNA is made from processed mRNA with reverse transcriptase, so it lacks introns and can be expressed in bacteria.

Why is "A genomic fragment containing the introns" not the answer?

Introns in genomic DNA would not be spliced out in bacteria.

Why is "The promoter region alone" not the answer?

A promoter does not encode the protein.

Why is "Satellite DNA from the centromere" not the answer?

Satellite DNA is non-coding repetitive sequence.

What concept does this question test?

It tests Molecular biology and genetics: cDNA cloning in Biochemistry. Genomic DNA would retain introns that bacteria cannot remove. A promoter alone contains no coding sequence.

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: cDNA cloning?

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.