Identification: RFLP versus PCR methods: practice question

A Forensic Medicine 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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Forensic Medicine · Identification: RFLP versus PCR methods

Sample item

Which DNA typing method needs a relatively large amount of intact, high-molecular-weight DNA, limiting its use on tiny or degraded forensic samples?

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

The answer and the reasoning

A. Restriction fragment length polymorphism (RFLP)

RFLP cuts genomic DNA with restriction enzymes and detects long variable fragments by Southern blotting, which needs micrograms of good-quality DNA. PCR-based STR typing amplifies short fragments from nanogram amounts and has replaced it in practice.

Option by option

  • A. Restriction fragment length polymorphism (RFLP) (correct)

    Correct. RFLP needs large amounts of undegraded DNA.

  • B. Mitochondrial DNA sequencing

    Mitochondrial DNA is present in many copies per cell and is used for degraded samples.

  • C. Y-chromosome STR typing

    Y-STR typing uses PCR on small amounts of male DNA.

  • D. Short tandem repeat typing by PCR

    PCR-STR typing amplifies small amounts of DNA, including partly degraded samples.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is A, Restriction fragment length polymorphism (RFLP). RFLP cuts genomic DNA with restriction enzymes and detects long variable fragments by Southern blotting, which needs micrograms of good-quality DNA.

Why is "Mitochondrial DNA sequencing" not the answer?

Mitochondrial DNA is present in many copies per cell and is used for degraded samples.

Why is "Y-chromosome STR typing" not the answer?

Y-STR typing uses PCR on small amounts of male DNA.

Why is "Short tandem repeat typing by PCR" not the answer?

PCR-STR typing amplifies small amounts of DNA, including partly degraded samples.

What concept does this question test?

It tests Identification: RFLP versus PCR methods in Forensic Medicine. PCR-based STR typing amplifies short fragments from nanogram amounts and has replaced it in practice.

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 Identification: RFLP versus PCR methods?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.