PCR or the Polymerase Chain Reaction has become the
cornerstone of modern molecular biology the world over.
Real-time PCR is an advanced form of the Polymerase
Chain Reaction that maximizes the potential of the
technique.
To understand real time PCR it is easier to begin with
the principles of a basic PCR:
PCR is a technique for amplifying DNA. There are 2
reasons why you may want to amplify DNA. Firstly you may
want to simply create multiple copies of a rare piece of
DNA. For example a forensic scientist may want to amplify
a tiny piece of DNA from a crime scene. More commonly
however you may wish to compare 2 different samples
of DNA to see which is the more abundant. DNA analysis
requires amplification in order for there to be enough DNA
to give a detectable signal for quantification. If you amplify
both samples at the same rate, you can calculate which
sample had the highest copy number of the target of
interest to begin with.
It is a thermostable polymerase enzyme that drives a PCR.
A polymerase will synthesize a complementary sequence
of bases to any single strand of DNA providing it has a
double stranded starting point.
This is very useful because you can choose which gene
you wish the polymerase to amplify in a mixed DNA sample
by adding small pieces of DNA complimentary to your
gene of interest. These small pieces of DNA are known as
primers because they prime the DNA sample ready for the
polymerase to bind and begin copying the gene of interest.