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1. Polymerase chain reaction
(PCR)
Prepared by
Hawre najmaddin
Zahra govand
Omer fariq
Blimat Kamran
Bushra tarq
Super visor :Dr. Ahmad Nawzad Hassan
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2. Outline
• Introduction
• Principles
• Components Of PCR
• The steps of PCR
• Applications of PCR
• Advantages, disadvantage
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3. Introduction
• Polymerase chain reaction (PCR) is a common
laboratory technique used to make many copies
(millions or billions!) of a particular region of DNA.
This DNA region can be anything the experimenter is
interested in.
• PCR is used in many areas of biology and medicine,
including molecular biology research, medical
diagnostics, and even some branches of ecology.
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4. Principles
• Typically, the goal of PCR is to make enough of the target DNA region
that it can be analyzed or used in some other way. For instance, DNA
amplified by PCR may be sent for sequencing, visualized by gel
electrophoresis, or cloned into a plasmid for further experiments.
• he PCR technique is based on the enzymatic replication of DNA. In PCR, a
short segment of DNA is amplified using primer mediated enzymes. DNA
Polymerase synthesises new strands of DNA complementary to the template
DNA. The DNA polymerase can add a nucleotide to the pre-existing 3’-OH
group only. Therefore, a primer is required. Thus, more nucleotides are added
to the 3’ prime end of the DNA polymerase.
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5. Components Of PCR
• Components Of PCR constitutes the following:
1.DNA Template– The DNA of interest from the sample.
2.DNA Polymerase– Taq Polymerase is used. It is thermostable and
does not denature at very high temperatures.
3.Oligonucleotide Primers- These are the short stretches of single-
stranded DNA complementary to the 3’ ends of sense and anti-sense
strands.
4.Deoxyribonucleotide triphosphate– These provide energy for
polymerization and are the building blocks for the synthesis of DNA.
These are single units of bases.
5.Buffer System– Magnesium and Potassium provide optimum
conditions for DNA denaturation and renaturation. It is also important
for fidelity, polymerase activity, and stability.
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6. The steps of PCR
• • PCR proceeds in THREE distinct steps Governed by Temperature:
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7. Applications of PCR
• The following are the applications of PCR :
• Medicine
Testing of genetic disease mutations. Monitoring the gene in gene therapy.Detecting disease-causing genes
in the parents.
• Forensic Science
Used as a tool in genetic fingerprinting. Identifying the criminal from millions of people.Paternity tests
• Research and Genetics
Compare the genome of two organisms in genomic studies. In the phylogenetic analysis of DNA from any
source such as fossils. Analysis of gene expression. Gene Mapping
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8. Advantages, disadvantage
Advantages of PCR Testing
• Valuable for detecting specific pathogens that are difficult to culture
in vitro or require a long cultivation period
• Significantly more rapid in providing results compared to culturing o
Enables earlier informed decision making o Rapid diagnosis of
bacteremia, particularly for low levels of bacteria in specimens
• Useful in detecting cases in extra pulmonary specimens which may
be missed by smear and/or culture Valuable screening tool o PCR is
still considered an adjunct test for certain diagnostic tests that still
rely on smear and culture, such as tuberculosis
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9. disadvantage
• Supply costs, machinery fees, training expenses
• Potentially lower specificity compared to culture and staining
• Since specific primers are used to identify different
microorganisms, physicians often need to list potential
microorganisms before performing selective PCR
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