geNorm output charts of M and V values for the 32 selected reference genes in 24 samples. (A) Stepwise exclusion of the least stable genes (lowest average expression stability measure M). The x-axis from left to right indicates the ranking of the genes according to their expression stability (M). (B) Determination of the optimal number of control genes for accurate normalization calculated on the basis of pair-wise variation (V) analysis. 1 = V2/3...........30 = V31/32.