Molecular biology and genetics: Turner syndrome: 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 · Molecular biology and genetics: Turner syndrome

Sample item

A 15-year-old girl has short stature, a webbed neck, widely spaced nipples, primary amenorrhoea and a bicuspid aortic valve. Which karyotype and hormonal finding are expected?

A45,X karyotype with low FSH from hypothalamic failureB46,XY karyotype with raised testosterone from androgen insensitivityC45,X karyotype with raised FSH from streak gonadsD47,XXX karyotype with normal FSH and ovarian function

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

The answer and the reasoning

C. 45,X karyotype with raised FSH from streak gonads

Turner syndrome is most often 45,X. Ovarian follicles are lost early, leaving streak gonads, so oestrogen is low and FSH and LH are raised (hypergonadotropic hypogonadism). Associated lesions include bicuspid aortic valve, coarctation and horseshoe kidney.

Option by option

A. 45,X karyotype with low FSH from hypothalamic failure
Gonadotropins are raised, not low, because the gonads have failed.
B. 46,XY karyotype with raised testosterone from androgen insensitivity
Androgen insensitivity gives a 46,XY girl with primary amenorrhoea but no webbed neck or short stature.
C. 45,X karyotype with raised FSH from streak gonads (correct)
Correct. 45,X with streak gonads gives high FSH and primary amenorrhoea.
D. 47,XXX karyotype with normal FSH and ovarian function
47,XXX women are usually tall with normal fertility and do not show this picture.

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, 45,X karyotype with raised FSH from streak gonads. Turner syndrome is most often 45,X.

Why is "45,X karyotype with low FSH from hypothalamic failure" not the answer?

Gonadotropins are raised, not low, because the gonads have failed.

Why is "46,XY karyotype with raised testosterone from androgen insensitivity" not the answer?

Androgen insensitivity gives a 46,XY girl with primary amenorrhoea but no webbed neck or short stature.

Why is "47,XXX karyotype with normal FSH and ovarian function" not the answer?

47,XXX women are usually tall with normal fertility and do not show this picture.

What concept does this question test?

It tests Molecular biology and genetics: Turner syndrome in Biochemistry. Ovarian follicles are lost early, leaving streak gonads, so oestrogen is low and FSH and LH are raised (hypergonadotropic hypogonadism). Associated lesions include bicuspid aortic valve, coarctation and horseshoe kidney.

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 Molecular biology and genetics: Turner syndrome?

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.