<Li> a DNA polymerase, an enzyme that polymerizes new DNA strands; heat - resistant Taq polymerase is especially common, as it is more likely to remain intact during the high - temperature DNA denaturation process </Li> <Li> two DNA primers that are complementary to the 3' (three prime) ends of each of the sense and anti-sense strands of the DNA target (DNA polymerase can only bind to and elongate from a double - stranded region of DNA; without primers there is no double - stranded initiation site at which the polymerase can bind); specific primers that are complementary to the DNA target region are selected beforehand, and are often custom - made in a laboratory or purchased from commercial biochemical suppliers </Li> <Li> deoxynucleoside triphosphates, or dNTPs (sometimes called "deoxynucleotide triphosphates"; nucleotides containing triphosphate groups), the building blocks from which the DNA polymerase synthesizes a new DNA strand </Li> <Li> a buffer solution providing a suitable chemical environment for optimum activity and stability of the DNA polymerase </Li>

How limited pcr is in comparison to cellular dna replication