A pool of 5,896 haploid-convertible heterozygous diploid yeast knockout (YKO) strains were transformed with a sgs1D::URA3 cassette. The resultant diploid double YKO pool was sporulated and the spores were spread on MM with 0.1% 5-FOA (as target source1) and MM-Ura (as target source2). Pools of haploid YKOs were harvested after incubation at 30 degree for 2 days. Genomic DNA samples were prepared from these two haploid pools and used as the templates for PCR amplification of the TAGs identifying the YKOs with a pair of primers universal for either Uptags or Downtags. The PCR products from sample1 were labeled with Cy5 and those from sample2 with Cy3. The Cy5- and Cy3-labeled Uptags and Downtags were mixed together and hybridized to a Rosetta_UpTag. Fluorescent array images were collected for both Cy5 and Cy3 with a GenePix4000B microarray scanner. The image data was annalyzed with the Imagene 5.0 and Genesight 3.1 programs from Biodiscovery. Keywords = sgs1D, dSLAM, heterozygotes, YKO