A view of the microarray. The array is composed of 32 grids of 420 spots each. A total of ca. 200 empty spots are distributed through the array for background controls. Probe spots are deposited in close duplicates. A set of PCR products and synthetic oligonucleotides was selected as controls. These include scorecard kits (Amersham Biosciences) in grids 4, 8, 12, 16, 20, 24, 28, and 32; serial dilutions of the signal normalization luciferase gene (row 1 in grids 3, 7, 11, 15, 19, 23, 27, 31) for which control RNA spike (Promega) can be obtained; 10 long oligonucleotides covering YKL182w (6153 bp) and 9 long oligonucleotides covering YLR310c (4767 bp) ORFs as controls for reverse transcription efficiency; 10 intergenic regions, 10 intronic sequences, and mitochondrial genes, 20 non-monotonous trinucleotide repeats (72-mer oligonucleotides) and 4 serial dilutions (in grid 1, 4, 29 and 32) of the total genomic DNA from the wild-type strain S288c; 3 E. coli genes (tuf A, ace F, kdt A) as negative controls; the LexA binding domain, the LacZ 5' and 3'end regions, the Pho4 binding domain, the Gal4 binding domain, the GFP, the TAP and GST as commonly used tags or reporter genes; Leu1, His5, and Ura4 from S. pombe, the humanCBF2 andc-myc genes, and the kanR gene as heterologous genes and markers. Printing buffer was deposited on the empty spots. The array shown results from hybridization with cDNA targets of total RNA isolated from wild-type BY4742 (Cy3-labelled) and Δydr225w (Cy5-labelled) strain.