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A man with a genetic mutation expresses a defective form of the cation channel r

ID: 3478519 • Letter: A

Question

A man with a genetic mutation expresses a defective form of the cation channel responsible for the “dark current” in the retina; the mutation renders his channels incapable of binding cGMP. Assume these mutant channels are only expressed in the outer segments of his rod photoreceptor cells. Which of the following would we reasonably expect?  Select any/all answers that apply.

He would be color-blind.

His visual acuity would be significantly impaired.

His rhodopsins would not get activated in the light.

His rod cells would have an abnormally low (hyperpolarized) resting membrane potential in the dark.

Intracellular cGMP levels would remain high, in the outer segments of his rod cells, regardless of variations in light levels.

A.

He would be color-blind.

B.

His visual acuity would be significantly impaired.

C.

His rhodopsins would not get activated in the light.

D.

His rod cells would have an abnormally low (hyperpolarized) resting membrane potential in the dark.

E.

Intracellular cGMP levels would remain high, in the outer segments of his rod cells, regardless of variations in light levels.

Explanation / Answer

D.his rod cells would have an abnormally low (hyperpolarized) resting membrance potentinal in the dark  

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