Introns and Splicing

[vixen]

Hi,
I have been studying for my biochem all day and there is something that I have been trying to understand...but I don't seem to get it!! Can someone try and explain Introns and Splicing to me? In my Stryer book, they use the example of beta-globin of the hemoglobin gene...does anyone know how to explain the splicing, introns, exons and how this stuff happens...continuous genes and discontinous genes? Thanks

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[Scooby Doo]

I can give you a basics of it...but I don't know all the details you probably want. This will probably be too basic for ya...

So we have DNA.

DNA is transcribed to RNA that includes all introns and exons.
This mess of RNA is then cut up by ??? and the introns go bye-bye. All that remains are the exons which is what the meat and potatoes of your DNA really is. This RNA (which only contains exons) is then transLATED into protein via tRNA's and all that fun stuff. Let's see an example:

Here's a random sequence of DNA (using fake bases)

AAAAQQQQQQBBBBBBBBQQQQQQQQQCCCCCCCCCQQQQQQQQQ

So take all the "Q's" as intronic sequence. (The main thing the intron is important for is signaling where the splicing can occur but that is too much in detail for this explanation.)
So when you transCRIBE the basic DNA into RNA, we get the same sequence (except for switching T's to U's).

So our RNA sequence is the same.
Now we splice out the introns and we get:

AAAABBBBBBBBCCCCCCCCC

This can then be transLATED into protein and make an enzyme to detoxify the alcohol we drink.

HOWEVER, humans have the wonderful ability to mix and match. Sooo, we could also get out:

AAAACCCCCCCC
and
BBBBBBCCCCCCCC
and
AAAA
and
BBBBBB
and
CCCCCCCC

So just from that one sequence we found that there are many types of proteins that can be made! This is why the human genome is not much longer than say that of fly or something. Everything is condensed.

Since you said you are taking biochem I am sure you already knew all this and I probably just wasted my time
You probably want exacts....and I just can't remember it b/c my brain doesn't function anymore.

 

[Amy]

Exactly how much detail are you looking for? I have a degree in molecular genetics, so I can probably help you out, but I'm not sure what you're looking for. Scooby did a good job explaining the basics. Remember also that the RNA forms a lariat structure in order to splice the introns.... the 2 ends of the intron come together and get spliced out, and then the 2 exons ligate together. Good luck with biochem...

 

[vixen]

Oh you guys are f@cking awesome...thanks so much scooby for the basics...this book is so descriptive, I can't understand it if I don't understand the basics...this is what I needed...now I can plug in the details from here...thanks guys!

 

[slptodoc]

Hey there,
There's a GREAT book that you might find very helpful, it's called "Clinical Biochemistry Made Ridiculously Simple" by Stephen Goldberg, M.D.
(around $22.oo)

You can get it through:
MedMaster, Inc.
p.o. box 640028
Miami, Fla 33164

There is a whole series of these books. I found out how valuable they were when I was taking my neuro classes in grad school!

I think you can get these over the net as well.

Hope this helps!

Good luck!
L