AAMC Question I got wrong about membrane receptors

[phattestlewt]

An autosomal recessive, nonlethal mutation (deletion) of the AcH receptor gene occurs in some rats. Which of the following organelles will most likely be abnormal in the rats having this mutation?

A. Microtubules (eliminated)
B. Ribosomes (eliminated)
C. ER
D. Plasma Membrane

The correct answer is Plasma membrane, but I put ER.

Someone walk me through how a plasma membrane protein is made? I thought that such proteins were synthesized in the Rough ER and so a dysfunctional ER would mean that it wouldn't properly be synthesized.

I understand how plasma membrane makes sense, but I went to the root of the synthesis and thought that ER would be more probable.
Whats up with that? Was I wrong in thinking that?

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[bluebillion]

The problem is not with the synthesis of the protein. it is because the gene that encodes for the protein itself doesn't exist. so the only organelle that will end up being affected is the plasma membrane, in the sense that it won't have the receptor there.

You are right in thinking that the ER is involved in the synthesis of proteins for the ER. but in this case it is not that the ER is messing up, it is because the gene doesn't exist.

 

[Fedxup]

Agree.
The problem is with the gene. The ER is functioning as it should. Since receptors are usually found on the plasma membrane, the mutated receptor will affect the plasma membrane.

 

[phattestlewt]

How do you know the gene doesn't exist?

Because the Q says it's a deletion mutation? But doesn't a deletion mutation mean the gene/protein is dysfunctional, not that the gene doesn't exist.

 

[jonhamm]

Whatever it is, it is a loss of function mutation in the receptor, not in the ER. Since the ER is not dependent on the function of the receptor for its own proper functioning, the ER will not be abnormal.

 

[phattestlewt]

Whatever it is, it is a loss of function mutation in the receptor, not in the ER. Since the ER is not dependent on the function of the receptor for its own proper functioning, the ER will not be abnormal.

Okay, I can see that. Thanks