annealing and extension in a conventional polymerase chain reaction a dna segment to be copied is first denatured into single strands by heating to 95 u00b0 c excess amounts of two synthetic oligonucleotides complementary to the 3 u2032 ends of the dna strands are added to the denatured dna and the mixture incubated by lowering the temperature to the annealing point 50 60 u00b0 c at this temperature the oligomers hybridize with the dna strands the hybridized oligonucleotides serve as primers for dna chain synthesis which begins upon addition to the reaction mixture of deoxynucleotides and a temperature resistant dna polymerase such as taq polymerase when synthesis is complete the mixture is reheated to the denaturation temperature to melt the newly formed dna duplexes lowering the temperature causes the oligomers which are still at a high relative concentration to bind to the denatured dna strands and another round of synthesis takes place in accordance with the present invention modulators are used to control the pcr reaction either by direct local heating of the subject molecules or simply through dispersion in the reaction mixture in the former case modulators are linked to the primer oligomers and the temperature of the reaction mixture is maintained at the incubation point following dna synthesis the excitation field is applied dehybridizing the newly formed duplexes because the reaction mixture as a whole remains at the incubation temperature the next cycle of synthesis begins as soon as the field is deactivated and this sequence is repeated to produce the desired degree of amplification the use of modulators to directly heat the molecules being amplified in a nucleic acid amplification reaction.