(a) Intra-array reproducibility was estimated from two representative array experiments performed simultaneously (one standard and one dye-swap). Standard deviation (STD) and coefficient of variation (CV) of Log2 signal ratios were calculated for each measurable triplicate spots, and the mean values of all repeated measurements were computed for each array. The median of mean STDs and CVs obtained from the two arrays are indicated. (b) Inter-array reproducibility as determined from 10 arrays performed at two distinct time periods (5 standard and 5 dye-swap). Median STD and CV were calculated from the mean Log2 signal ratios obtained for each measurable gene over the series of arrays.