Polymerase Chain Reaction (PCR) (College Board AP® Biology)

Polymerase Chain Reaction (PCR)

• Polymerase chain reaction (PCR) is a common molecular biology technique used in most applications of gene technology, for example, DNA profiling (eg. identification of criminals and determining paternity) or genetic engineering

• It can be described as the in vitro method of DNA amplification

• It is used to produce large quantities of specific fragments of DNA or RNA from very small quantities (even just one molecule of DNA or RNA)

  • By using PCR scientists can have billions of identical copies of the DNA or RNA sample within a few hours

• The PCR process involves three key stages per cycle

• In each cycle the DNA is doubled so in a standard run of 20 cycles a million DNA molecules are produced

• The three stages are undertaken in a PCR instrument (or thermal cycler) which automatically provides the optimal temperature for each stage and controls the length of time spent at each stage

Application of PCR

• Amplification of DNA and RNA through the PCR process provides quantities of DNA which can be analyzed further

• In biotechnology, amplified DNA is required, for example, to allow

  • DNA analysis in forensic science

  • The study of molecular phylogeny and classification