A specific DNA segment is amplified using the Polymerase Chain Reaction (PCR) method from a complicated mixture of starting material known as template DNA. The starting material, including the sample matrix and accessibility of target DNA, affects the sample preparation and purification methods. Most of the time, just minimum DNA purification is necessary, and some procedures, such direct PCR or extraction-free PCR, don't even need to purify their DNA or RNA first. Yet for Polymerase Chain Reaction (PCR) to work, it does need to know the DNA sequence details surrounding the DNA fragment that has to be amplified (called target DNA). Practically speaking, a PCR experiment is simple to do and can be finished in a few hours.
In general, a PCR reaction needs five key reagents:
· DNA to be amplified
· DNA polymerase
· Primers
· Deoxynucleotide triphosphates (dNTPs)
· PCR buffer
The strength of Polymerase Chain Reaction (PCR) comes from the exponential growth in DNA produced by repeated cycles of DNA synthesis using primers that flank a specific region, one primer directed at directing synthesis complementary to the top strand and the other primer directed at directing synthesis complementary to the bottom strand. The amount of DNA that is produced in each cycle increases by roughly a factor of two when this is done repeatedly. As a result, with enough cycles, the amount of DNA from the amplified area can be increased by a million-fold. The polymerase chain reaction gets its name from the fact that this exponential increase in abundance resembles a chemical chain reaction.
In the first cycle, the reaction template is the only one available, and it is still a significant template in the second cycle. A product with ends determined by primers is created at the conclusion of the second cycle. This is the desired outcome, and it acts as the primary model for the subsequent cycles. Although the original template is still there and can still be utilised, it does not experience the exponential growth seen for the desired product.
