Polymerase Chain Reaction (PCR)

Purpose of PCR

• Amplification of DNA: PCR allows for the amplification of DNA, turning a small sample into over a trillion copies.
  • Essential for analysis when only a small amount of DNA is available.
  • Widely used in various fields such as forensic microbiology, paternity testing, zoology, and archaeology.

Process of PCR

1. Denaturation

   • Temperature: DNA is incubated at a specific temperature (not provided in transcript).
   • Purpose: Breaks hydrogen bonds, separating double-stranded DNA into single strands.

2. Priming

   • Enzyme: DNA polymerase from thermophilic bacteria like Thermus aquaticus is used to withstand high temperatures without denaturing.
   • Primer: Serves as the starting point for DNA synthesis and localizes the amplification to the desired DNA segment.
   • Nucleotides: Necessary building blocks for DNA synthesis (A's, C's, G's, T's).

3. Extension

   • Temperature: Primers attach at another specific temperature (not provided in transcript).
   • Function: DNA polymerase reads the template strand and synthesizes a complementary strand.
   • Direction: DNA synthesized in the 5’ to 3’ direction.

Cycle of PCR

• Complete Cycle: Each cycle consists of denaturation, primer annealing, and extension.
• Amplification: Each cycle doubles the amount of DNA.
  • Example: 1 becomes 2, 2 becomes 4, 4 becomes 8, etc.

Applications of PCR

• Infectious Diseases: Detecting infectious agents in small samples.
• Drug-Resistant Bacteria: Identifying strains without needing to culture them.
• Genetic Research: Enables work with DNA across various scientific fields.