4.4.1 Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA

Why might we want to amplify minute quantities of DNA?

Polymerase chain reaction is a laboratory technique that is used to copy DNA (basically used to amplify small quantities of DNA). The machine used to make copies of the DNA is called the thermocycler (a device used to amplify segments of DNA via the PCR)

Image of a thermocycler:

Image source: http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Pcr_machine.jpg/220px-Pcr_machine.jpg

This process is useful when only a small amount of DNA is available but a large quantity is needed so that tests can be done on it. 

A real life example of when only a small amount of DNA is available but a large quantity is needed is in forensics. Where perhaps only a small amount of blood or tissue is found at a crime scene and a lot of tests needs to be done on them (or some of the DNA needs to be given to the defense so that they can run their own tests for verification). 

It is in this situation where it would be useful to amplify small quantities of DNA. 

INTERESTING NOTE: PCR requires high temperatures and a DNA polymerase enzyme that we can get from Thermus aquaticus (which is a bacteria that lives in hot springs) 

Citation: http://www.ibguides.com/biology/notes/genetic-engineering-and-biotechnology