PCR Summary (A-Level 2nd Year)

Polymerase Chain Reaction (PCR)


 Invitro gene cloning method
 Produce many copies of DNA at will
 Ingredients for DNA replication… DNA, DNA Helicase, Free Nucleotides, DNA
Polymerase.



DNA REPLICATION:
1) DNA helicase unzips DNA, by breaking H Bonds, this separates DNA molecule into 2
template strands
2) Activated nucleotides join by complementary base pairing (A, T, C, G) to 2 template
strands, H bonds form
3) DNA Polymerase (Can only attach to double stranded DNA) joins sugar phosphate
backbone by forming phosphodiester bonds between nucleotides; does NOT reform H
bonds
4) Semi Conservative replication: new DNA Molecules made up of 1 new and 1 original
strand
5) Each molecule forms a double helix



PCR + DNA REPLICATION
 Don’t need to use the enzyme DNA Helicase + could just heat up DNA to split DNA into 2
templates required for DNA Replication



Ingredients for PCR
 DNA Fragment (needs copying)
 Free nucleotides
 DNA Polymerase
 Primer (small piece of single stranded DNA, complementary to a sequence on another
piece of single stranded DNA)
 Heat (95 degrees)