Cell Biology Practice Test: Techniques in Cell Biology - Polymerase Chain Reaction — Flashcards

Polymerase chain reaction (PCR) is a technique that quickly makes millions to billions of copies of a DNA sample. It's based on the principle of enzymatic replication of nucleic acids. 

PCR is a basic method for DNA analysis and has revolutionized recombinant DNA technology. It's used to construct recombinant molecules by preparing a desired DNA fragment in large quantities. The PCR-amplified DNA is then cloned into a vector of choice. 
PCR works by using DNA polymerase's ability to synthesize a new DNA strand that's complementary to a template strand. The number of copies doubles after each cycle, and usually 25 to 30 cycles produce enough DNA. 
The PCR process is automated and can be completed in a few hours. A machine called a thermocycler alters the reaction's temperature every few minutes to allow DNA denaturing and synthesis. 

The steps of PCR are:
Denaturation: Heat the reaction to separate the DNA strands.
Annealing: Cool the reaction so the primers can bind to their complementary sequences on the single-stranded template DNA. 

To perform PCR, the template is mixed with primers, Taq polymerase, and nucleotides. The mixture is heated to 94°C to denature the DNA duplex.