The PCR technique provides highly specific and sensitive means for analyzing nucleic acids, but it does not allow their direct quantification. This limitation originates from the fact that the efficiency of PCR depends on the amount of template sequence present in the sample, and the amplification is exponential only at low template concentrations (1 ). Because of this “plateau effect” of the PCR, the amount of the amplification product does not directly reflect the original amount of the template. Moreover, subtle differences in the reaction conditions, such as material from biological samples, might cause significant sample to sample variation in the final yield of the PCR product.
