mRNA and protein detection

[Tonino]

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I have a practice passage and this part makes no sense to me.
It has nothing to do with the questions, but it caught my eye..

it says that they couldn't detect any mRNA for a receptor, yet they've found proteins of it.

How is this possible? Any rational explanation?

 

[flodhi1]

I have a practice passage and this part makes no sense to me.
It has nothing to do with the questions, but it caught my eye..

it says that they couldn't detect any mRNA for a receptor, yet they've found proteins of it.

How is this possible? Any rational explanation?

Well if the mRNA was translated to proteins wouldn't the mRNA not be present anymore. Let's say I have 10 dollars and I spend 10 dollars in buying lunch. Now I don't hate 10 bucks. You have mRNA and you spend (translate) it to protein now you won't have the mRNA present anymore because it became a protein? make sense?

 

[stsa84]

Well if the mRNA was translated to proteins wouldn't the mRNA not be present anymore. Let's say I have 10 dollars and I spend 10 dollars in buying lunch. Now I don't hate 10 bucks. You have mRNA and you spend (translate) it to protein now you won't have the mRNA present anymore because it became a protein? make sense?

What?? That's not how it works! mRNA doesn't transform into a protein any more than the blueprints of house magically turn into the house itself. mRNA acts as instructions to assemble a protein from free amino acids. I hope you have a lot of time to study before taking the MCAT...

Receptors are usually single proteins or protein complexes. The passage is saying that the receptor itself has been discovered, but they have not been able to identify or isolate the mRNA that codes for the proteins that make up the receptor.

 

[gunj122]

Well if the mRNA was translated to proteins wouldn't the mRNA not be present anymore. Let's say I have 10 dollars and I spend 10 dollars in buying lunch. Now I don't hate 10 bucks. You have mRNA and you spend (translate) it to protein now you won't have the mRNA present anymore because it became a protein? make sense?

um this is not true. mRNA is not transformed into protein, it's just an instruction manual for the cell to put together individual amino acids.

anyway, this is kind of an odd situation. i would say the protein might have been from an exogenous organism. for example, maybe the cell endocytosed a foreign pathogen and now expresses its proteins but does not contain its mRNA. idk =/ that's my theory.

would you mind posting the related question and the answer choices so we could better understand what the passage was hinting at? it's difficult to postulate reasons when we don't have the passage to work with.

 

[BilalL]

Maybe its relating to the fact that mRNA has an extremely short half life (1-3 minutes)?

 

[Tonino]

thanks for the responses guys.
I can't repost it because it's in my textbook and it would take me too long to type it all.. but I guess your explanations are valid. Thanks again for your help.

 

[salim271]

Maybe its relating to the fact that mRNA has an extremely short half life (1-3 minutes)?

^I agree with this. mRNA is degraded too fast to reliably be tracked. Proteins can have much longer life spans and can be found.

 

[flodhi1]

What?? That's not how it works! mRNA doesn't transform into a protein any more than the blueprints of house magically turn into the house itself. mRNA acts as instructions to assemble a protein from free amino acids. I hope you have a lot of time to study before taking the MCAT...

Receptors are usually single proteins or protein complexes. The passage is saying that the receptor itself has been discovered, but they have not been able to identify or isolate the mRNA that codes for the proteins that make up the receptor.

I already took it lol and scored a 1 on each section......yes I messed that up a little...... I did not mean to say that the mRNA was spent I was trying to say that it's purpose is used up therefore the body does not require it anymore. And yeah mRNA is degraded the quickest in the human body. Sorry I used the wrong example in the end to explain it haha loL@it's spent.

 

[stsa84]

I already took it lol and scored a 1 on each section......yes I messed that up a little...... I did not mean to say that the mRNA was spent I was trying to say that it's purpose is used up therefore the body does not require it anymore. And yeah mRNA is degraded the quickest in the human body. Sorry I used the wrong example in the end to explain it haha loL@it's spent.

Eek, hope that was a typo

 

[flodhi1]

Eek, hope that was a typo

Guy I was being sarcastic. I scored close to my low 30s average and my AAMC average for the BS was a 12. I slipped on this fundamentally basic concept, it's been a month and half since I got done, give a brother a break through these stressful times lol

 

[addo]

What?? That's not how it works! mRNA doesn't transform into a protein any more than the blueprints of house magically turn into the house itself. mRNA acts as instructions to assemble a protein from free amino acids. I hope you have a lot of time to study before taking the MCAT...

Receptors are usually single proteins or protein complexes. The passage is saying that the receptor itself has been discovered, but they have not been able to identify or isolate the mRNA that codes for the proteins that make up the receptor.

well yea.... once you finish the house, you dont really need the blueprint anymore. unless youre making more of the same houses.

if the cell doesnt need to keep on expressing the mrna for the given receptor, the mrna will simply degrade, and no more transcription will take place either

 

[MD Odyssey]

Just to pile on the bandwagon here, the probable reason that no mRNA was found is lifetime within the cell. But, the lifetime for an mRNA isn't always 1-2 minutes. It varies a lot, but many mRNA can exist in the cell for hours, particularly in eukaryotes.

 

[MD Odyssey]

if the cell doesnt need to keep on expressing the mrna for the given receptor, the mrna will simply degrade, and no more transcription will take place either

This is somewhat misleading, since it implies that if the cell is going to continue expressing a particular gene, then the mRNA will NOT degrade. This is incorrect. Degradation will occur regardless of whether the cell is expressing that gene or not. But if transcription is blocked, then no more mRNA will be produced.

Also, we shouldn't be so quick to think that a lack of expression for a particular gene implies that transcription doesn't occur. There are lots of ways to regulate expression of a gene and not all of them inhibit transcription.