Reproduction: testis-determining gene: practice question

A Physiology 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.

Try it

Physiology · Reproduction: testis-determining gene

Sample item

A 17-year-old with female external genitalia has primary amenorrhoea, no breast development, a uterus and tubes on ultrasound, streak gonads and a 46,XY karyotype. Which gene defect is most likely?

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

The answer and the reasoning

A. Absent or mutated SRY gene

The SRY gene on the Y chromosome directs the gonad to become a testis. Without it the gonads fail and become streaks, so there is no anti-Mullerian hormone or testosterone. Mullerian structures persist, the genitalia are female and there is no puberty.

Option by option

  • A. Absent or mutated SRY gene (correct)

    Correct. Without SRY the testes do not form, so neither anti-Mullerian hormone nor androgens are made.

  • B. Androgen receptor gene mutation

    Androgen insensitivity has normal testes making anti-Mullerian hormone, so there is no uterus.

  • C. Anti-Mullerian hormone receptor gene mutation

    An anti-Mullerian receptor defect gives a male phenotype with a retained uterus, not female genitalia.

  • D. Steroid 5-alpha-reductase type 2 gene mutation

    5-alpha-reductase deficiency has testes and Mullerian regression, with virilisation at puberty.

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 Physiology questions

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Absent or mutated SRY gene. The SRY gene on the Y chromosome directs the gonad to become a testis.

Why is "Androgen receptor gene mutation" not the answer?

Androgen insensitivity has normal testes making anti-Mullerian hormone, so there is no uterus.

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

An anti-Mullerian receptor defect gives a male phenotype with a retained uterus, not female genitalia.

Why is "Steroid 5-alpha-reductase type 2 gene mutation" not the answer?

5-alpha-reductase deficiency has testes and Mullerian regression, with virilisation at puberty.

What concept does this question test?

It tests Reproduction: testis-determining gene in Physiology. Without it the gonads fail and become streaks, so there is no anti-Mullerian hormone or testosterone. Mullerian structures persist, the genitalia are female and there is no puberty.

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 Reproduction: testis-determining gene?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.