general question about PCR

Austin P. So (Hae-Jin) haejin at netinfo.ubc.caX
Sat Nov 13 04:28:12 EST 1999

The bands that you get are defined by the primers you choose. Your template
is presumably genomic DNA. Your two primers are complementary to regions of
the genomic DNA, probably flanking the gene you are playing with. Thus when
you perform your PCR, you will amplify the DNA within these two primer
regions, which will be the band that you see. You will get two bands for a
heterozygous mouse (usually). If you don't understand why, then you should
look up inheritance. You cannot amplify the whole genome because it is too
big for the polymerase to handle and the genome consists of many strands of
DNA and PCR absolutely depends on the presence of primers.

This really should be in any basic textbook....but not spelled out to you
exactly as you want it. Maybe you should review your understanding of how
the PCR reaction actually works.

jennnn1970 at wrote:

> I understand the process of collecting tail DNA, making of primers, the
> thermalcycles and such. I just don't understand how you'd get a bunch
> of fragments to run on a gel at the end of the PCR?
> Do you digest the genomic dna first? Do you digest the PCR'd DNA at the
> end? Do the primers only extend so far?
> I don't understand why the PCR reaction wouldn't copy the WHOLE piece
> of DNA.

Austin P. So (Hae Jin)

Biotechnology Laboratory
University of British Columbia

E-mail: haejin at (under construction)

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