Genetics: Hardy-Weinberg calculation: 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 · Genetics: Hardy-Weinberg calculation

Sample item

An autosomal recessive disorder occurs in 1 in 10,000 births in a population in Hardy-Weinberg equilibrium. What is the approximate carrier frequency?

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

The answer and the reasoning

D. About 1 in 50

If q squared is 1/10,000, then q is 1/100 or 0.01, and p is 0.99. Carrier frequency is 2pq, which is 2 x 0.99 x 0.01 = 0.0198, or about 1 in 50. Carriers are therefore far more common than affected people.

Option by option

  • A. About 1 in 10

    A carrier frequency of 1 in 10 would give an incidence of about 1 in 400, far higher than stated.

  • B. About 1 in 5,000

    This merely doubles the disease incidence and has no basis in the Hardy-Weinberg equation.

  • C. About 1 in 100

    This is the allele frequency q (1 in 100), not the carrier frequency, which is about double.

  • D. About 1 in 50 (correct)

    Correct. 2pq = 2 x 0.99 x 0.01 = 0.0198, about 1 in 50.

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, About 1 in 50. If q squared is 1/10,000, then q is 1/100 or 0.

Why is "About 1 in 10" not the answer?

A carrier frequency of 1 in 10 would give an incidence of about 1 in 400, far higher than stated.

Why is "About 1 in 5,000" not the answer?

This merely doubles the disease incidence and has no basis in the Hardy-Weinberg equation.

Why is "About 1 in 100" not the answer?

This is the allele frequency q (1 in 100), not the carrier frequency, which is about double.

What concept does this question test?

It tests Genetics: Hardy-Weinberg calculation in Anatomy. 01, and p is 0.99. Carrier frequency is 2pq, which is 2 x 0.99 x 0.01 = 0.0198, or about 1 in 50. Carriers are therefore far more common than affected people.

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 Genetics: Hardy-Weinberg calculation?

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.