Relative expression of gene cassettes in the Vibrio sp . DAT722 array. The bar graph indicates the relative expression of each gene cassette using gDNA as an internal standard. The vertical axis indicates the level of expression while the horizontal axis indicates position within the cassette array. The schematic cassette array below the histogram indicates cassette positions within the array detected in gDNA, with solid triangles. Cassette positions not detectable with the methodology used are shown in dotted triangles. Cassettes that are ambiguously located within the array by the methodology used, due to the presence of either multiple copies of the same cassette within the array, or different cassettes of the same size, are indicated by blue rectangles. Putative expression blocs, as referred to in the text are shown by pink rectangles.