Medical genetics: Rett syndrome: 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 · Medical genetics: Rett syndrome

Sample item

A girl develops normally until 12 months and then loses purposeful hand use, develops hand-wringing movements, seizures and deceleration of head growth. Which gene is mutated?

AFMR1 on the X chromosomeBMECP2 on the X chromosomeCSMN1 on chromosome 5DUBE3A on chromosome 15

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

The answer and the reasoning

B. MECP2 on the X chromosome

Rett syndrome is an X-linked dominant disorder caused by mutations in MECP2, which encodes a methyl-CpG binding protein. It occurs almost exclusively in girls, since most affected males die early.

Option by option

A. FMR1 on the X chromosome
FMR1 expansion causes fragile X syndrome.
B. MECP2 on the X chromosome (correct)
Correct. MECP2 mutation causes Rett syndrome.
C. SMN1 on chromosome 5
SMN1 deletion causes spinal muscular atrophy.
D. UBE3A on chromosome 15
UBE3A loss causes Angelman syndrome.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is B, MECP2 on the X chromosome. Rett syndrome is an X-linked dominant disorder caused by mutations in MECP2, which encodes a methyl-CpG binding protein.

Why is "FMR1 on the X chromosome" not the answer?

FMR1 expansion causes fragile X syndrome.

Why is "SMN1 on chromosome 5" not the answer?

SMN1 deletion causes spinal muscular atrophy.

Why is "UBE3A on chromosome 15" not the answer?

UBE3A loss causes Angelman syndrome.

What concept does this question test?

It tests Medical genetics: Rett syndrome in Anatomy. It occurs almost exclusively in girls, since most affected males die early.

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 Medical genetics: Rett syndrome?

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.