Taq polymerase replicating DNA, molecular model. The Taq polymerase is blue, the two strands of DNA are green, and the nucleotide bases are grey (carbon), pink (nitrogen), yellow (oxygen and green (phosphorus). Taq polymerase is a DNA polymerase derived from the heat-resistant bacterium Thermus aquaticus. It is an enzyme that plays a crucial role in DNA replication. It reads one strand of DNA and builds up the complementary sequence of nucleotides on another strand. Taq polymerase is widely used in the polymerase chain reaction (PCR), a biochemical technique for mass production of a portion of DNA. This requires high temperatures, meaning only heat-stable polymerases such as Taq can be used.