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
Exam Tip
The details of the PCR technique is beyond the scope of the AP Exam, although you should familiarize yourself with the concept of PCR and where it is used / what it is used for.
