Hybridization of total RNA and in vitro transcribed RNA standards. (A) Representative microarray image of total RNA from HeLa cells, in vitro transcribed U11 and U12 snRNA. Total RNA or in vitro transcribed snRNAs of the same RNA sample, labeled with Alexa647 (red) and Alexa546 (green), were hybridized at 48°C. Yellow signifies an overlap of green and red fluorescence. Dotted circles indicate the probe locations for U11 and U12 snRNAs. (B) Total RNA labeled with Alexa647 was hybridized at six different amounts: 50, 100, 250, 500, 1000 and 2500 ng. The heat maps are shown for all probes on the array with signals twofold above background. The 250 ng sample signals were set at 1 (black) while the range covered −10 fold (green) to +10 fold (red).