Step I Protein Expression & Northern Blot

[bbpiano1]

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I've gotten a few questions basically asking, "Which technique could be used as a measure of Gene X's expression?" The answer is always Northern blot, but wouldn't Western blot be better? With a Northern, you don't know if the mRNA is being translated successfully. Any thoughts on this discrepancy?

 

[TerpMD]

I've gotten a few questions basically asking, "Which technique could be used as a measure of Gene X's expression?" The answer is always Northern blot, but wouldn't Western blot be better? With a Northern, you don't know if the mRNA is being translated successfully. Any thoughts on this discrepancy?

I wondered about that too but I think its because when they say gene expression the most proximal measure of that is mRNA. I think because protein expression can be affected by other things along the way it less directly associated with expression of the gene (though for most purposes one would think that is what you care about more....)

 

[RussianJoo]

Here's the way I think about it... They're baiscally asking you if you know what the product of gene expression is, or they're even asking you what the word "Gene" means. By definition a gene is a segment of DNA. or genes are found on DNA and when expressed make RNA. so how do you measure RNA? with a Northern Blot. When you're picking Western blot as an answer choice, you're not answering the question they're asking.. You're answering the question "how do you measure RNA expression?"


That's how the USMLE gets you, you know the answer but pick the wrong one. That's why I think the test is pretty simple as long as you can quickly break down the question and ask yourself exactly what they're asking.

 

[Rogue Synapse]

Plus, there are a lot of things in between gene expression and functional protein. I take expression to mean "Is this gene transcribed into mRNA?", but you also have to worry about splicing, translation, posttranslational modifications, and so on. When I was in grad school, I worked on the mRNA expression and actual protein concentrations of one gene and got very different stories.