Question

How many molecules of DNA would result from one molecule after four cycles of PCR?

A. 16
B. 4
C. 2
D. 32

Answer 1

A.16 is the answer.....

It is because, it gets double at every stage....2^4 = 16.

Answer 2

A. 16

Step-by-step explanation:

The PCR technique is based on the amplification - in vitro - of a single DNA sequence millions of times. Basically it makes several copies of the fragment of interest of the DNA that will be studied.

PCR occurs in three steps and they all depend on a temperature gradient.

• 1st step: Denaturation (at 95ºC) of the double strand of DNA, which occurs due to the rise in temperature.
• 2nd step: Priming (57ºC to 63ºC) of the primers, which can occur in a temperature variation between 57ºC to 63ºC.
• 3rd step: Extension (at 72ºC) with the operation of Taq Polymerase, which helps in the introduction of nucleotides that will complement the chain being synthesized.

The three steps together form one cycle, a normal PCR has around 36 cycles. As each DNa molecule will form 2 new molecules it is possible how many DNA molecules a single DNA molecule will form in each cycle. To do this, you must calculate "2^n", where "n" corresponds to the number of cycles.

So, to know how many DNA molecules would result from a molecule after four cycles of PCR, you have to calculate 2^4 = 16 molecules.