Embryology: sex determination: practice question

A Anatomy 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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Anatomy · Embryology: sex determination

Sample item

A phenotypic female has primary amenorrhoea, a normal uterus and streak gonads, and a 46,XY karyotype. Which gene is most likely mutated?

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

The answer and the reasoning

D. SRY

Loss of the testis-determining SRY gene means the gonads do not form testes, so there is no anti-Mullerian hormone or testosterone. The uterus and tubes persist and the external genitalia are female, as in Swyer syndrome.

Option by option

  • A. SRD5A2

    SRD5A2 deficiency leaves testes and causes ambiguous genitalia that virilise at puberty.

  • B. Anti-Mullerian hormone gene

    Anti-Mullerian hormone gene loss gives a male phenotype with persistent Mullerian structures.

  • C. Androgen receptor gene

    Androgen receptor defects leave functioning testes that secrete anti-Mullerian hormone, so no uterus is present.

  • D. SRY (correct)

    Correct. Loss of SRY leaves streak gonads and a female phenotype in a 46,XY individual.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is D, SRY. Loss of the testis-determining SRY gene means the gonads do not form testes, so there is no anti-Mullerian hormone or testosterone.

Why is "SRD5A2" not the answer?

SRD5A2 deficiency leaves testes and causes ambiguous genitalia that virilise at puberty.

Why is "Anti-Mullerian hormone gene" not the answer?

Anti-Mullerian hormone gene loss gives a male phenotype with persistent Mullerian structures.

Why is "Androgen receptor gene" not the answer?

Androgen receptor defects leave functioning testes that secrete anti-Mullerian hormone, so no uterus is present.

What concept does this question test?

It tests Embryology: sex determination in Anatomy. The uterus and tubes persist and the external genitalia are female, as in Swyer syndrome.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Embryology: sex determination?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.