Identification: amelogenin sex typing: 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: amelogenin sex typing

Sample item

DNA from the tooth pulp of a burnt, unidentified body is amplified at the amelogenin locus and electrophoresis shows two peaks differing by a few base pairs. What does this indicate?

AThe sex cannot be stated without a Y-STR profileBThe individual is male, since the X and Y products differ in sizeCThe individual is male, since two peaks mean two X chromosomesDThe individual is female, since two X chromosomes give two different alleles

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

The answer and the reasoning

B. The individual is male, since the X and Y products differ in size

The amelogenin gene is present on both sex chromosomes, and the Y copy yields a product of a different size from the X copy. A male therefore shows two peaks, while a female shows one. Amelogenin typing is a standard sex marker in forensic DNA profiles.

Option by option

A. The sex cannot be stated without a Y-STR profile
The X and Y amelogenin products are distinguishable, so sex can be stated without Y-STRs.
B. The individual is male, since the X and Y products differ in size (correct)
Correct. Two products of different size mean one X and one Y.
C. The individual is male, since two peaks mean two X chromosomes
Two X chromosomes would give one peak, not two.
D. The individual is female, since two X chromosomes give two different alleles
Two X chromosomes give identical products, so a female shows a single peak.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is B, The individual is male, since the X and Y products differ in size. The amelogenin gene is present on both sex chromosomes, and the Y copy yields a product of a different size from the X copy.

Why is "The sex cannot be stated without a Y-STR profile" not the answer?

The X and Y amelogenin products are distinguishable, so sex can be stated without Y-STRs.

Why is "The individual is male, since two peaks mean two X chromosomes" not the answer?

Two X chromosomes would give one peak, not two.

Why is "The individual is female, since two X chromosomes give two different…" not the answer?

Two X chromosomes give identical products, so a female shows a single peak.

What concept does this question test?

It tests Identification: amelogenin sex typing in Forensic Medicine. A male therefore shows two peaks, while a female shows one. Amelogenin typing is a standard sex marker in forensic DNA profiles.

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: amelogenin sex typing?

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.