a method for amplifying oligonucleotide in vitro by polymerase - endonuclease chain reaction which utilizes a single - stranded dna probe containing repeat sequences , extends a target oligonucleotide by a thermostable dna polymerase , cleaves extended products with a thermostable endonuclease , and amplifies target oligonucleotide by thermocycling . in pecr , a specific oligonucleotide is exponentially amplified using one single probe instead of a pair of primers , and the reaction is precisely controlled by thermal cycles whose parameters are flexibly adjustable according to length , sequence , melting temperature and initial amount of the target oligonucleotide . amplification speed depends totally on initial amount of target oligonucleotide present in the reaction system . the method can be used to amplify specific small nucleic acids , such as oligonucleotides and micrornas , and further conduct quantitative analysis . pecr is easy to conduct with high efficiency , specificity and stability , and thus can be widely used in molecular biology studies .