Figure 5.

Effect of SAGE mRNA count on coefficient of variation, average absolute log ratio, and signal intensity. SAGE yields data on the absolute expression level, in counts of mRNA per cell, of genes. A) The coefficient of variation estimated for a given gene does not generally appear to depend upon the absolute expression level. B) The average absolute log ratio does not generally appear to depend upon the absolute expression level. C) Intensity of a microarray spot does depend upon absolute expression level, at least for highly abundant genes. Error bars are +/- 2 standard errors of the mean. Larger error bars at higher SAGE levels are due to smaller numbers of genes at those levels and do not reflect a greater standard deviation of the measurements.