The polymerase chain reaction (PCR) is an important technique for biology students to learn. PCR utilizes DNA polymerases isolated from archaea or bacteria, like Thermus aquaticus (Taq), to amplify target DNA sequences. In this paper we describe lab activities where students clone the gene for, express, and purify Taq DNA polymerase and assay for its activity. These lab activities employ plasmids containing multiple components of the lac operon thereby giving students practical experience with a genetic regulatory system they learn about in the classroom. Taq DNA polymerase purification simply involves cell lysis, a heat incubation step, and centrifugation, with the resulting supernatant containing highly pure and active Taq DNA polymerase.