Polymerase Chain Reaction(PCR)

Julie McDonaldAlli Hicks

Courtney Dailey

Polymerase Chain Reaction

• How is it used?– Medical and

biological research for a variety of applications

– DNA cloning, functional analysis of genes, diagnosis of hereditary diseases, genetic fingerprints (forensic science and paternity testing) and the detection of infectious diseases.

PCR

• Used to amplify (replicate) a single piece of DNA– The original molecules are replicated by

the DNA polymerase enzyme: doubles the number of DNA molecules (cycle)• a cycle is repeated many times resulting in

a “chain reaction”

–Makes it possible to amplify a piece of DNA: creating millions of copies of the original

Polymerase Chain Reaction

• A single segment is taken from a DNA sample to amplify

• The red segment is what is going to be replicated during PCR

Targeted DNA• The targeted

DNA includes around 20 nucleotides, DNA primers, and the enzyme TAQ which are all used during PCR

Cycle 1

• The cycle begins with heating up the DNA mixture to 95° Celsius – The heat denatures

the DNA and breaks up the hydrogen bonds that hold the strands together .

• The temp. is then reduced to 60° so the primers can form hydrogen bonds

Cycle 1 cont.

• Temp. is raised to 72° Celsius

• At this temperature polymerization begins adding nucleotides to the DNA strands

• There are two double stranded copies of the DNA after 1 cycle

Cycle 2• Temp is raised

to 95° again• after the 2nd

cycle there are 4 copies of the target DNA

Cycle 3• 8 copies of target DNA

are created after cycle 3

• The more cycles, the greater the proportion of fragments with just target DNA– Half of the fragments

consist of just target DNA and the other half also contains flanking DNA.

Cycle 4 & more

• 16 copies of the target DNA are created after cycle 4.

• With each cycle, the number of copies double

• There are on average 25 cycles– Over 33 million

copies of the target DN

PCR machines

• There are different types of machines • All have a system that allows it to

raise and lower the temperature of the DNA to allow PCR to occur

The PCR song!

• The PCR Song by Scientists for Better PCRThere was a time when to amplify DNA,You had to grow tons and tons of tiny cells.(Oooh) Then along came a guy named Dr. Kary Mullis,Said you can amplify in vitro just as well.Just mix your template with a buffer and some primers,Nucleotides and polymerases too.Denaturing, annealing, and extending,Well it’s amazing what heating and cooling and heating will do.[Chorus]PCR when you need to detect mutation (detect mutation)PCR when you need to recombine (recombine)PCR when you need to find out who the daddy is (who’s your daddy?)PCR when you need to solve a crime (solve a crime)[x2]