Estimates of absolute gene-expression level, in molecules per cell, assuming that the SAGE counts for each gene are typical of wild-type strains. The 95% credible intervals indicated are those for relative gene expression among samples, and do not incorporate sampling variance in the SAGE assay. (a) Acid phosphatase genes are similarly meagerly expressed in swi1Δ and snf2Δ mutants. (b) Acid phosphatase regulators PHO4 and PHO2 are not significantly differentially expressed in swi1Δ and snf2Δ mutants, so that Snf2p/Swi1p control may be direct. cDNA microarray measurements of PHO4 gene-expression levels show that it is not significantly abundant or meager in swi1Δ or snf2Δ mutants, even though a large SAGE assay could detect no transcript sequence tags for this gene. PHO4 expression level shown here was arbitrarily set to 0.1 molecules per cell, an order of magnitude below the experiment's detection threshold .