Molecular biology: 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

Sample item

Which base-pairing rule applies to double-stranded DNA?

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

The answer and the reasoning

A. Adenine pairs with thymine

In DNA, adenine forms two hydrogen bonds with thymine and guanine forms three with cytosine; this complementary pairing enables accurate replication and repair of genetic information.

Option by option

  • A. Adenine pairs with thymine (correct)

    Correct: adenine pairs with thymine in DNA.

  • B. Uracil pairs with guanine

    Uracil is mainly found in RNA rather than DNA.

  • C. Adenine pairs with cytosine

    Adenine does not normally pair with cytosine in standard DNA helices.

  • D. Guanine pairs with thymine

    Guanine pairs with cytosine, not thymine.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Adenine pairs with thymine. In DNA, adenine forms two hydrogen bonds with thymine and guanine forms three with cytosine; this complementary pairing enables accurate replication and repair of genetic information.

Why is "Uracil pairs with guanine" not the answer?

Uracil is mainly found in RNA rather than DNA.

Why is "Adenine pairs with cytosine" not the answer?

Adenine does not normally pair with cytosine in standard DNA helices.

Why is "Guanine pairs with thymine" not the answer?

Guanine pairs with cytosine, not thymine.

What concept does this question test?

It tests Molecular biology in Biochemistry. The correct option holds because: Correct: adenine pairs with thymine in DNA.

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?

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.