Official Guide B/B #9 (spoiler)

[663697]

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I was thinking of choosing D at first but I couldn't really reason my way through this one. Can somebody explain why A or B would be incorrect? I assumed that chloramphenicol didn't inhibit translation at a specific concentration or that the incubation time was too short. I'm not sure why these would be wrong and AAMC didn't really go in depth with their explanation.

 

[Nugester]

A, B, and C are all possible answers, but is it the best answer? They all involve changing variables involving chloramphenicol. That's a flag that none of those are the right answer. D is entirely different; use a different drug. That's how I'd approach the answer.

 

[663697]

A, B, and C are all possible answers, but is it the best answer? They all involve changing variables involving chloramphenicol. That's a flag that none of those are the right answer. D is entirely different; use a different drug. That's how I'd approach the answer.

So would it be correct to approach it by looking at the commonality between answer choices when it comes to these design questions? When I initially thought of choosing D I changed my mind because it sounded too simple 😛

Edit: Just checked the answer again and it says that cat is described as being an acetyltransferase of the drug, so it expected that we make the inference that acetylation = inactivation of the drug. I thought methylation caused inactivation and acetylation caused activation? Or is this only applicable to DNA?

 

[Nugester]

Is that the whole passage? If not, I don't think I'll be able to give a proper explanation as the paragraph you posted doesn't mention acetylation...

 

[663697]

Is that the whole passage? If not, I don't think I'll be able to give a proper explanation as the paragraph you posted doesn't mention acetylation...

 

[Nugester]

Oh, okay. So, based on the passage it states that the drug UNCOUPLES transcription and translation in E.Coli w/o Cat6xbs, while the drug FAILS to do that in E.Coli w/ Cat6xbs. Cat encodes an acetyltransferase; this implies that somehow acetyltransferase inhibits/de-activates the drug.

 

[663697]

Oh, okay. So, based on the passage it states that the drug UNCOUPLES transcription and translation in E.Coli w/o Cat6xbs, while the drug FAILS to do that in E.Coli w/ Cat6xbs. Cat encodes an acetyltransferase; this implies that somehow acetyltransferase inhibits/de-activates the drug.

Wow, I totally missed the part that said it uncouples transcription and translation in E.coli without Cat6xbs. Did you infer that from the first pic above (where it says "to characterize the mRNA element that targets the transcript to the membrane, scientists fused 6xbs..."? Ie. this was meant to say that first, they tried it out on E.coli without 6xbs and after inserting 6xbs they noticed a different effect? If that's the case the question becomes much easier to answer

 

[Nugester]

Exactly!