PCR And Its Use Essay, Research Paper

PCR And Its Use

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

The whole process is pretty much summed up like this: They heat up the DNA to

let the enzymes break it down (or ‘unzip’ its bonds). Then add specific amounts

of the primer (relative to the amount of DNA you have. Then you add the enzyme

to sets of 4 nuclotides that will go through the genetic sequence of nucleotides

and hook up the matching nucleotide (A goes to T and G to C etc). Keep adding 4

more after the enzymes finish with the one you just added it to.

When all this is done, there will no longer be a shortage of DNA, but an

abundant amount, so the tests can be properly run on it. PCR isn’t as difficult

to understand as it may seem at first, but it can be explained in a very simple

way:

C = Cytosine G = Guanine A = Adenine T = Thymine

You will now assume the role of a genetic scientist. Here is the little bit of

DNA that you have managed to obtain:

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

The PCR process will perform an artificial ‘protein synthesis’ in a way. It

(through heat) will break down the bonds that currently keep your specimin in

tact. It will, basically, just line up the nucleotides with their match, and

the two strands of the double helix will become two full strands of DNA. So,

the above code is the coding for one strand of your DNA sample. The PCR machine,

will in effect, match them up:

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

PCR has many uses. It can be used in criminal cases, when they only have a

fragment of a speck of blood to deal with. They can also use it to piece back

together the DNA of an ancient fossil of a dinosaur. The possibilites just

never seem to end with DNA. Until recently, there was no such thing as the PCR

or a PCR machine. You had to do things by hand and that really added to the

cost of research. In effect, not as many people heard about what was going on

in the world of DNA. People should be educated about DNA because if you know

about DNA it can be useful if you are ever called to jury duty and they are

using that kind of evidence. You will be able to make a wise decision.