A technique based on PCR to exponentially increase the number of copies of a specific DNA sequence in a quantitative manner. Since the number of molecules theoretically doubles in each PCR cycle, the number of amplification cycles combined with the final amount of PCR product should allow calculation of the initial quantity of genetic material. Two common methods of quantification are the use of fluorescent dyes that intercalate with double-strand DNA, and modified DNA probes that fluoresce when hybridized with a complementary DNA. The level of fluorescence can be followed in real time (i.e. with each amplification cycle).