Dye-flip hybridizations. (a) A histogram showing the distribution of all elements (as a percent of the total) as a function of axial symmetry of reflection (ASR, a ratio vs ratio plot, see text). This is a measure of the contribution of dye effects to the results of a heterotypic hybridization. (b) The ratio plotted against position of the element on the array. The dye-reversed hybridizations are coded blue or red. Note the symmetrical patterns of differential expression as well as the bulk non-differential expression at a ratio of 1 (0 in log space). Experiments were performed in quadruplicate.