SANTA CLARA, Calif.--GeneChip developer Affymetrix here and Roche Molecular Systems announced a joint effort to develop and market a new generation of diagnostic tests that combines Affymetrix's GeneChip DNA probe array technology with Roche's PCR gene amplification technology. The companies will initially develop diagnostic kits for applications in HIV drug resistance. The agreement provides a framework for the development of additional GeneChip diagnostic kits as the parties identify further product opportunities.