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|PCR - Polymerase Chain Reaction Forum PCR - Polymerase Chain Reaction Forum. Discuss and ask questions about PCR troubleshooting, PCR protocols and methods, PCR products, and PCR theory.|
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Starting with one double strand, how many double strands of DNA would you have
after 2 cycles of PCR? How do you get this answer?
and then can you use that to get the answer to these?
How many after 3 cycles?
How many after 4 cycles?
How many after 10 cycles?
How many after 20 cycles?
How many after 30 cycles?
The formula is:
x*(2^n), where n equals the number of cycles and x equals the starting number of double-stranded DNA molecules.
At the beginning (0 cycles), there's 1 molecule of DNA. 1*(2^0) = 1
After the first cycle, it's 1*(2^1) = 2 dsDNA molecules
After 30 cycles, it's 1*(2^30) = 1073741824 dsDNA molecules.
This assumes that each cycle is 100% efficient and none of the raw materials needed ever run out (i.e. primers and dNTPs).
Each cycle of PCR doubles that amount of double strands you have.
So if you started with 1 double strand of DNA.
Then after 1 cycle you would have: 1 * 2 = 2 double strands
after 2 cycles you would have 2 * 2 = 4 double strands
after 3 cycles you would have 4 * 2 = 8 double strands
after 4 cycles you would have 8 * 2 = 16 double strands
I hope by now you see the pattern. You can use simple algebra to express the above:
T = N * 2^C
Where T is your total number of double strands, N is your starting number of double strands and C is the number of cycles.
Hope this helps,
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