Subject: what part of DNA is amplified in PCR?

Hi
I do understand how PCR works.What I can't follow is why the ampliconsin PCR 
are exons.Aren't exons non coding sequences of DNA?If we amplify the exons 
then what are we acheiving?
Thanks
Geetha

Response:

Re: what part of DNA is  amplified in PCR?

Hi Geethakrb,

Thanks for submitting your question to the MadSci network. I think that 
you are laboring under two misconceptions.

First, the exons represent the EXpressed segements of a gene. It is the 
INTRONS that represent the INTeRvening sequences between the exons. 
Introns are the segments of DNA that are not expressed. 

Introns and Exons are found in genes, but there is much DNA that does not 
encode any genes. Most DNA is neither an intron nor an exon.

Second, the amplicons in PCR are not necessarily exons or introns. The 
amplicon is whatever happens to be between the primers that you are 
using. If the primers are in an intron, than the amplicon corresponds to 
an intron. If the primers are in an exon, then the amplicon corresponds 
to an exon. If one primer is in an exon and the other in an intron, then 
the amplicon will correspond to parts of both. I think you can see how 
this works. 

Finally, even though introns don't contain codons, it doesn't mean that 
they aren't interesting. For example, splice-variants that result in 
different introns being spliced out can result in different protein 
sequences. Introns can contain polymorphisms that are of interest from an 
evolutionary perspective, and can also contain regulatory elements.

Cheers,

Steve Mack, Moderator MadSci Network

_______________________________________________________________
Hi
I do understand how PCR works.What I can't follow is why the ampliconsin PCR 
are exons.Aren't exons non coding sequences of DNA?If we amplify the exons 
then what are we acheiving?
Thanks
Geetha


________________________________________________________________
MadSci Network
http://www.madsci.org/
webadmin@madsci.org