match the polymerase chain reaction (pcr) step to its accurate description. - denaturation - annealing - extension - expansion - centrifugation 1. not a step of pcr 2. not a step of pcr 3. dna polymerase builds a complementary dna strand 4. primers bind to the dna strands once the temperature is lowered. 5. temperature is elevated and the two dna strands are separated.
