Question

What are the three stages of PCR? What happens? At what temperature? What is Taq polymerase and why is it important? What are all the necessary reagents for PCR? What are primers and how do they bind?

Answer 1

PCR stands for polymerase chain reaction , has multiple applications. Used for amplifying DNA,a specific region from it, PCR uses the primers (single stranded DNA ,they flank the region to be copied and bind to the template DNA by complementary base pairing), Taq polymerase, template DNA (the DNA region to be copied) and nucelotides which extend the DNA copies, cofactors for the enzymes used, example magnesium ion for Taq polymerase.

The three stages of PCR are ;

Denaturation step wherein high temperature of around 95-97deg celsius is used to seperate the two DNA strands so a single stranded template DNA is available for copying.

Annealing step wherein the reaction is cooled to a range from 56-67 degree celsius enabling binding of primers to the complementary DNA template strands.

Extension step wherein the temperature is increased again to around 70-72 degree celsius so that Taq polymerase enzyme can extend the primers using nucleotides (DNA building blocks A,T,G.C) to make copies of the template DNA.

After one cycle of PCR , there are two copies of DNA (doubling). Multiple copies can be made depending upon the cycles of PCR run.

Taq polymerase is a thermostable enzyme and can withstand high temperature without denaturing . It functions best in the range og 70-73 degree celsius and extends the primers to make copies of DNA region of interest