Amplification in PCR

Taking into account the calculations above and that in theory only one target molecule is sufficient to be amplified in PCR, it is obvious that 1 jUg of soybean DNA does contain more than enough DNA. From a practical point of view it is usually recommended that the sample DNA be diluted rather than concentrating the DNA amount in PCR in order to get a positive signal. Failure of amplification in PCR is probably due to the presence and accumulation of inhibitors after extraction of DNA from samples rather than the low presence of target molecules. 

Figure 4 Polymerase chain reaction (PCR). (a) Principle of DNA amplification in PCR (b) a typical thermocycle in PCR. (Adapted from R.A. Gibbs. Anal. Chem. 62 1202-1214,1990. With permission.)...

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