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Ballard HS Protocols

Polymerase Chain Reaction

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	Polymerase Chain Reaction PCR Overview Master Mix Steps PCR Buffer Primers for PCR Primer Lengths MgCl₂ dNTPs Taq Polymerase PCR Steps Add Master Mix Thermocycler Overview Denature Anneal Extend Repeat

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The essence of the PCR process is that the more cycles you run, the more copies of your DNA fragment will be produced. After only one cycle, your DNA fragment is still not the right size, because only one end of the fragment has been bound by a primer. On the second cycle, you continue to get copies of the incorrect size fragment (see the first 4 cycles). Only after the third cycle do you begin to get copies of the correct size double-stranded DNA fragment. In order to get many copies, you must run several cycles:

Cycles	Total # of ds DNA pieces	Copies of the ds DNA Fragment you are ampifying
1	2	0
2	4	0
3	8	2
4	16	8
10	1,016	996
15	32,760	32,730
20	1,048,576	1,048,536
25	33,554,432	33,554,382
30	1,073,741,824	1,073,741,764

REMOVE PCR SAMPLE