Figure 1.

Overlapping probes show increased correlation between gene expression measurements produced by the Affymetrix Hu133A chip and the Agilent Human 1 cDNA microarray. Relative expression ratios were measured and calculated while comparing RNA from the cell cultures MDA-MB-436 and HMEC and from the cell cultures HCC1954 and HMEC. Aliquots of the same RNA sample were hybridized to different platforms. Relative expression was calculated at the level of individual probes on the Affymetrix platforms. Pearson correlation coefficients were calculated between ratios determined by individual Affymetrix probe intensities and the ratios obtained from cDNA microarray. Correlation coefficients were determined for different subsets of probes including overlapping PM, overlapping MM, non-overlapping PM and non-overlapping MM.