A molecular testing device comprises a heating and cooling module having a thin-film thermoelectric heating and cooling device, and a removable test module having a combined amplification and hybridization reaction chamber. The reaction chamber comprises a thermo-conductive exterior surface and a microarray on an interior surface. The thin-film thermoelectric heating and cooling device has a heat transfer surface that is adapted to make contact with the thermo-conductive exterior surface of the reaction chamber. The molecular testing device may be used to perform a PCR in the reaction chamber.