PCR What is PCR polymerase chain reaction It is amethod to

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					What is PCR(polymerase chain reaction)

It is amethod to analyze ashort sequence of DNAor RNA even in
samples containing only minute quantitiesof them

Advantages of PCR
Amplification of selected sequences of DNA or RNA in few hours
rather than cloning the sequences of the interest into vectors for
expression which may take several weeks

Highly effiency&accurancy as PCR uses the same molecules that the
nature uses for coping DNA
       Two "primers", short single-stranded DNA sequences
     that are synthesized to correspond to the beginning and
     ending of the DNA stretch to be copied;

       An enzyme called polymerase that moves along the
     segment of DNA, reading its code and assembling a copy;

       A pile of DNA building blocks that the polymerase needs
     to make that copy.

How is PCR (polymerase chain reaction) done?
1.     Denaturation: At 94 C (201.2 F), the double-stranded
     DNA melts and opens into two pieces of single-stranded

2.       Annealing: At medium temperatures, around 54 C (129.2
     F), the primers pair up (anneal) with the single-stranded
     "template" (The template is the sequence of DNA to be
     copied.) On the small length of double-stranded DNA (the
     joined primer and template), the polymerase attaches and
     starts copying the template.

3.      Extension: At 72 C (161.6 F), the polymerase works best,
     and DNA building blocks complementary to the template
     are coupled to the primer, making a double stranded
     DNA molecule.

With one cycle, a single segment of double-stranded DNA
template is amplified into two separate pieces of double-
stranded DNA. These two pieces are then available for
amplification in the next cycle. As the cycles are repeated,
more and more copies are generated and the number of
copies of the template is increased exponentially.
What is the purpose of doing a PCR
(polymerase chain reaction)?

To do PCR, the original DNA that one wishes to copy need not
be pure or abundant. It can be pure but it also can be a minute
part of a mixture of materials. So, PCR has found widespread
and innumerable uses -- to diagnose genetic diseases, do
DNA fingerprinting, find bacteria and viruses, study
humanevolution, clone the DNA of an Egyptian mummy,
establish paternity or biological relationships, etc..
Accordingly, PCR has become an essential tool for
biologists,DNA forensics labs, and many other laboratories
that study genetic material.
How was PCR (polymerase chain reaction)
PCR was invented by Kary Mullis. At the time he thought up
PCR in 1983, Mullis was working in Emeryville, California for
Cetus, one of the firstbiotechnology companies. There, he
was charged with making short chains of DNA for other
scientists. Mullis has written that he conceived of PCR while
cruising along the Pacific Coast Highway 128 one night on his
motorcycle. He was playing in his mind with a new way of
analyzing changes (mutations) in DNA when he realized that
he had instead invented a method of amplifying any DNA
region. Mullis has said that before his motorcycle trip was
over, he was already savoring the prospects of a Nobel Prize.
He shared the Nobel Prize in chemistry with Michael Smith in
As Mullis has written in the Scientific American: "Beginning
with a single molecule of the genetic material DNA, the PCR
can generate 100 billion similar molecules in an afternoon. The
reaction is easy to execute. It requires no more than a test tube, a few simple reagents,
and a source of heat."

What is RT PCR?
RT-PCR (Reverse transcriptase-polymerase chain reaction) is
a highly sensitive technique for the detection and quantitation
of mRNA (messenger RNA). The technique consists of two
      The synthesis of cDNA(complementary DNA) from RNA
    by reverse transcription (RT) and
      The amplification of a specific cDNA by the polymerase
    chain reaction (PCR).
RT-PCR has been used to measure viral load with HIV and
may also be used with other RNA viruses such
as measles and mumps.

Role of PCR
in diagnosis of infectious diseases
Detect antimicrobial resistance
Detect microbes can not be cultivated
Measurement value of viral load
ment value of viral load

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