Figure 1.

Array design and comparative hybridization principle. The Pseudomonas aeruginosa Tiling Array (PATA1) includes ~215000 DNA oligonucleotide probes of 25 bp (black bars). Placed with variable probe spacing (24 – 34 bp) these probes cover 85.9% of the PAO1 genome leaving gaps of up to 9 bp (average ~4). For comparative hybridization, labeled DNA fragments of a reference strain (dark green) and the test strain (light green) were hybridized in parallel to separate PATA1 arrays. Signal ratios were calculated for each oligonucleotide as log₂ ratio of test versus reference signal and can e.g. be visualized by the Integrated Genome Browser (IGB). Genetic variations lead to mismatches of sample and probe DNA and hence to a decrease in signal ratio.