A glance at PCR

1. Polymerase Chain Reaction
(PCR)
Mohammed Esawie, M.D., M.S.(c)

2. Background
• DNA amplification techniques produce
thousands or million copies of a particular
gene
• Either: In-vitro  PCR
In-vivo  Molecular Cloning
• In short: seek and find the gene  amplify it

4. PCR
• Definition??!
• Components:
1- Target DNA
2- Nucleotides
3- DNA polymerase
4- Primers

5. STEPS of PCR (Temperature)
- for one cycle
95 ◦c
(for one min.)
• Denaturation: to break hydrogen
bonds pairing the 2 DNA strands
55 ◦c
(for one min.)
• Annealing: the primers are allowed to
bind to DNA
72 ◦c
(for 3 min.)
• Extension: DNA polymerase makes use
of nucleotides to elongate the gene

6. STEPS of PCR (Temperature)
- for one cycle

7. PCR Cycles
If we begin with one copy of the gene
After (n) cycles: The number of copies = 2n

8. REAL TIME PCR (RT-PCR)
• For RNA
• One added step before PCR: Complementary
DNA (cDNA) by reverse transcriptase (RT)
enzyme

10. PCR Uses
• Diagnosis of infectious diseases:
Pathogens unable to grow in culture:
Ex: Hepatitis B virus (HBV), hepatitis C virus (HCV)
Pathogens slowly grow in culture:
Ex: Mycobacterium Tuberculosis
• Forensic Testing:
By amplification of DNA from a dried blood spot or
one hair follicle to trace the accused person

11. Image Credits
• www.yourgenome.org
• www.sciencelearn.org.nz

12. Thank You