laczlacylaci

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I understand the question in general but I was wondering if someone could explain what technique D is.

upload_2016-8-5_22-57-58.png

What does it mean by pull down?
I am assuming this is effective because certain proteins (identified by mass spectrometry) is only localized at certain places in the cell?
 

aldol16

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Pulldown is exactly what it sounds like. You put a tag on the protein (via gene manipulation) - His tags are common - and "pull it down" afterwards using the handle. So if you put a His tag on the protein, you can pass it through a Ni column to take it out. That's an easy first step for purification.

And then after you pull it down, you're going to have pulled down the protein of interest plus any other proteins it's bound to. So if you do the mass spec, you can determine the weight of the whole complex and guess at what proteins are in there.

Is D the correct answer? Because D isn't very effective vis-a-vis the other options. Pulldown doesn't usually tell you where the protein is but the nature of the interacting proteins might - no guarantees though.
 

bobeanie95

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I think B might be the better answer. I would reason that since you know the protein it binds to, you would have a general idea of where the protein could be located (ie. mitochondria, golgi complex, etc). In the case of the rb transcript, you can't really gain any useful information since all transcripts will initially begin translation in the cytosol.
 
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aldol16

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I think B might be the better answer. I would reason that since you know the protein it binds to, you would have a general idea of where the protein could be located (ie. mitochondria, golgi complex, etc). In the case of the rb transcript, you can't really gain any useful information since all transcripts will initially begin transcription in the cytosol.
When does transcription ever begin in the cytosol...?
 
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laczlacylaci

laczlacylaci

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Sorry! The correct answer is B because the q-stem is trying to locate the pRB, which is a protein. If we put a tag on the rb transcript, which is the mRNA, the tag could be spliced out during the process of translation.

What do you guys think the reason why D is effective? Do you think knowing the interaction proteins would tell you where the pRB would be? Like only certain proteins are located at certain locations?
 

bobeanie95

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Sorry! The correct answer is B because the q-stem is trying to locate the pRB, which is a protein. If we put a tag on the rb transcript, which is the mRNA, the tag could be spliced out during the process of translation.

What do you guys think the reason why D is effective? Do you think knowing the interaction proteins would tell you where the pRB would be? Like only certain proteins are located at certain locations?
This is not the case for every protein but some could be localized predominantly in one organelle. For example, let's say pRB bound to Complex IV (Electron transport chain). This would give you a hint that pRB is located within the mitochondria.
 

theonlytycrane

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What do you guys think the reason why D is effective? Do you think knowing the interaction proteins would tell you where the pRB would be? Like only certain proteins are located at certain locations?
If we see that pRB interacts with some other proteins that we know about we could infer that maybe pRB hangs out with them in their specific part of the cell.
 

aldol16

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What do you guys think the reason why D is effective? Do you think knowing the interaction proteins would tell you where the pRB would be? Like only certain proteins are located at certain locations?
It wouldn't be a guarantee but if the protein(s) it interacts with is localized, then you would know immediately one place pRB goes. So for instance, if pRB binds to a membrane protein, then you know that it localizes to the membrane. But this is the "perfect" experiment. A more likely result would be seeing it not bound to another protein or not knowing the protein it binds to.
 

betterfuture

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Sorry to bump this thread but AAMC's "the answer is C because *restating what C said* and because it's C" explanations are not helping. Why is the answer B and not C?
 

neppywise

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*bump* how exactly do we know rb transcripts are in the cytosol, since they are hardly mentioned in the passage?
 

aldol16

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*bump* how exactly do we know rb transcripts are in the cytosol, since they are hardly mentioned in the passage?
Transcripts are generally in the cytosol... because that's where they have to be for translation to occur. The only time they're in the nucleus is when they're being made.