Often times, scientists only have a small amount of DNA to deal with when doing
genetic research or studies. In these situations, scientists can do one of
several things. One is to just try to work with it anyway, but this is nearly
impossible (depending on how much there is). Ther are a couple other processes
they can use, or they can use PCR. PCR is one of the more complicated, but
reliable ways to do tests on DNA when they only have a small amount to begin
with. PCR, or Polymearse Chain Reaction, is the scientific process used by
genetic scientists to clone DNA.

"A 'rapid diagnostic' technique used in the clinical microbiology lab to detect
pathogens. It relies upon amplification technology utilizingthe heat stable DNA
polymerase from a thermophilic organism." (from
http://www.genes.com/pcr/pcrinfo.html) Dr. K.Mullis recently received the Nobel
prize for inventing the technique.

This is how they go about doing this: They first get their small DNA sample.
Then they mix all the chemicals (this includes the primer, etc). Then they have
to run it through the PCR machine. Here is a (rather detailed) description of
the process: "The cycling protocol consisted of 25-30 cycles of three-
temperatures: strand denaturation at 95degC, primer annealing at 55degC, and
primer extension at 72deg C, typically 30 seconds, 30 seconds, and 60 seconds
for the DNA Thermal Cycler and 4 seconds, 10 seconds, and 60 seconds for the
Thermal Cycler 9600, respectively."

Basically, that means that they set it to certain temperatures, then put it in
different cyles for different amounts of time. PCR machines can be compared
with washing machines. There are the different temperatures (here for example,
there is 72degC, where in the washing machine you would set it to cold/cold
respectively.

For it to properly replicate, we must know how to match each of the following:

A T G A T A T G G C A G C A A C G A C C A T A

the match would be

T A C T A T ...