A pool of 5,896 haploid-convertible heterozygous diploid yeast knockout (YKO) strains were sporulated A pool of isogenic haploid MATa cells were obtained by selection on a magic medium with (sample2) or without (sample1) 15 microgram/ml of benomyl at 30 degree for 3 days. Genomic DNA samples were prepared from these two pools of freshly generated haploid cells 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 Hopkins-TagArray. Fluorescent array images were collected for both Cy5 and Cy3 with a GenePix4000B microarray scanner. The image data was annalyzed with a GenePix5.1 program. Keywords = 15 microgram/ml, benomyl, heterozygotes, YKO