Colour vision: inheritance: practice question

A Ophthalmology 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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Ophthalmology · Colour vision: inheritance

Sample item

A boy is unable to distinguish red from green and his maternal grandfather has the same problem. What is the inheritance?

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

The answer and the reasoning

D. X-linked recessive

Red-green colour deficiency arises from opsin gene defects on the X chromosome and is far commoner in males. Deuteranomaly is the commonest form.

Option by option

  • A. Mitochondrial

    Mitochondrial inheritance is maternal and affects both sexes.

  • B. Autosomal recessive

    Autosomal recessive would not favour males.

  • C. Autosomal dominant

    Autosomal dominant would affect both sexes through generations.

  • D. X-linked recessive (correct)

    Correct. Skipping through a carrier mother is typical of X-linked recessive inheritance.

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 Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is D, X-linked recessive. Red-green colour deficiency arises from opsin gene defects on the X chromosome and is far commoner in males.

Why is "Mitochondrial" not the answer?

Mitochondrial inheritance is maternal and affects both sexes.

Why is "Autosomal recessive" not the answer?

Autosomal recessive would not favour males.

Why is "Autosomal dominant" not the answer?

Autosomal dominant would affect both sexes through generations.

What concept does this question test?

It tests Colour vision: inheritance in Ophthalmology. Deuteranomaly is the commonest form.

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 Colour vision: inheritance?

Group the red eye by what to examine and what the pupil does. Then use the flashcards and the other Ophthalmology 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.