DNA replication: eukaryotic polymerases: 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 · DNA replication: eukaryotic polymerases

Sample item

A researcher inactivates the eukaryotic polymerase that extends Okazaki fragments with the help of the sliding clamp PCNA. Unligated short fragments accumulate. Which polymerase was inactivated?

ADNA polymerase gammaBDNA polymerase epsilonCDNA polymerase deltaDDNA polymerase beta

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

The answer and the reasoning

C. DNA polymerase delta

In eukaryotes polymerase alpha-primase starts each strand, polymerase delta extends the lagging strand with PCNA and polymerase epsilon extends the leading strand. Polymerase delta works with FEN1 and ligase to process Okazaki fragments. Beta is a repair enzyme and gamma replicates mitochondrial DNA.

Option by option

A. DNA polymerase gamma
Polymerase gamma replicates mitochondrial DNA only.
B. DNA polymerase epsilon
Polymerase epsilon is the main leading strand enzyme.
C. DNA polymerase delta (correct)
Correct. Polymerase delta synthesises the lagging strand.
D. DNA polymerase beta
Polymerase beta functions in base excision repair, not in replication.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, DNA polymerase delta. In eukaryotes polymerase alpha-primase starts each strand, polymerase delta extends the lagging strand with PCNA and polymerase epsilon extends the leading strand.

Why is "DNA polymerase gamma" not the answer?

Polymerase gamma replicates mitochondrial DNA only.

Why is "DNA polymerase epsilon" not the answer?

Polymerase epsilon is the main leading strand enzyme.

Why is "DNA polymerase beta" not the answer?

Polymerase beta functions in base excision repair, not in replication.

What concept does this question test?

It tests DNA replication: eukaryotic polymerases in Biochemistry. Polymerase delta works with FEN1 and ligase to process Okazaki fragments. Beta is a repair enzyme and gamma replicates mitochondrial 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 DNA replication: eukaryotic polymerases?

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.