Molecular biology: PCR: 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: PCR

Sample item

Which component is required in polymerase chain reaction to synthesize new DNA strands at high temperature?

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

The answer and the reasoning

A. Thermostable DNA polymerase

PCR uses a thermostable DNA polymerase, such as Taq polymerase, so repeated denaturation cycles do not destroy enzymatic activity. Primers define the amplified target sequence.

Option by option

  • A. Thermostable DNA polymerase (correct)

    Correct. A heat-stable polymerase enables repeated high-temperature cycling.

  • B. RNA polymerase II

    RNA polymerase II transcribes eukaryotic mRNA.

  • C. DNA ligase only

    Ligase is not the DNA-synthesizing enzyme in PCR.

  • D. Reverse transcriptase only

    Reverse transcriptase is used when starting from RNA in RT-PCR.

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 A, Thermostable DNA polymerase. PCR uses a thermostable DNA polymerase, such as Taq polymerase, so repeated denaturation cycles do not destroy enzymatic activity.

Why is "RNA polymerase II" not the answer?

RNA polymerase II transcribes eukaryotic mRNA.

Why is "DNA ligase only" not the answer?

Ligase is not the DNA-synthesizing enzyme in PCR.

Why is "Reverse transcriptase only" not the answer?

Reverse transcriptase is used when starting from RNA in RT-PCR.

What concept does this question test?

It tests Molecular biology: PCR in Biochemistry. Primers define the amplified target 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: PCR?

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.