3. Retinitis pigmentosa (RP) is a genetic disorder that causes the loss of visio

Question

3. Retinitis pigmentosa (RP) is a genetic disorder that causes the loss of vision which affects 1 in 4,000 people. It has been discovered that RP can be caused by mutations in rhodopsin. A patient with deteriorating eyesight comes in to see you. This patient also tells you that they have a family history of blindness. You decide to sequence this patient's rhodopsin gene and you find that they have a deleterious mutation in their rhodopsin gene. List a possible mutation in rhodopsin this patient could have and explain how the mutation could affect the patient's ability to see in terms of how the signaling to the brain will be affected.

Explanation / Answer

Rhodopsin is the visual pigment present in the rods, and absorption of light by this pigment brings conformational changes to its structure and activates it. Absorption of light by rhodopsin converts the cis-retinal to trans-retinal, and the color of retinal changes from purple to yellow, this reaction is called “bleaching or isomerization.” In dark, trans-retinal is converted to cis-retinal and is called “regeneration of photopigment.”

The patient might have a missense or nonsense mutation in the gene coding for rhodopsin, which results in either an abnormally functional or non-functional protein. This mutation can either directly interfere with the activity of rhodopsin or its transport tot he disc membranes, thus, impair the process of vision. Rhodopsin is an important molecule in the phototransduction process. Rhodopsin activation in the rids causes closure of the sodium gated channels and hyperpolarize the photoreceptor.

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