Comparison of M. tuberculosis 70-mer oligonucleotide array set printed in the presence or absence of 5'-fluorescein-labeled tracking oligonucleotide. A: Single sub array images of the M. tuberculosis 70-mer oligonucleotide array set printed in the presence (panels I, fluorescein; and II, Cy3/Cy5) or absence (panel III, Cy3/Cy5) of 5'-fluorescein-labled tracking oligonucleotide. Black arrowheads, denote rows containing tracking oligonucleotide only, note high fluorescein intensity (Panel I) and lack of cross-hybridization with labeled target (Panel 2). Images shown in panel I and panel II are the same array before and after hybridization. B: Scatter plot of mean Cy3/Cy5 log intensity ratios of fluorescence from hybridized arrays printed in the absence (x-axis) or presence (y-axis) of 5'-fluorescein-labeled tracking oligonucleotide.