- can be used to amplify millions of copies of DNA
1. a reaction mixture is set up that contains the DNA sample, free nucleotides, primers and DNA polymerase.
primers - are sohrt pieces of DNA that complementary to the bases at the start of the fragment you want.
DNA polymerase is an enzymes that creates new DNA strands
2. DNA mixture is heated to 95 degrees to break down hydrogen bonds between the two strands of DNA. this is important as it means many cycles of PCR can be carried out without having to use a new enzyme everytime
3. mixture cooled to 50-60 so primer can bind to strands
4. reaction mixture is heated to 72 so DNA polymerase can work
5. DNA polymerase lines up free DNA nucleotides alongside each template strand, complementary base pairing means new complementary strands are formed.
6. 2 new copies of fragments DNA are formed are one cycle of PCR is complete
7. cycle starts again but mixture kept at 95 this time all 4 strands used as templates (2 old 2 new)
8. each PCR cycle doubles the amount of DNA ( 1= 2x2=4, 2 =4x2=8, 3=8x2=16 and so on)
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