Quantitative and qualitative analyses based on <i>geNorm</i>.

<p>A) Pairwise variation (V) analysis. <i>geNorm</i> first calculates an expression stability value (M) for each gene and then compares the pair-wise variation (V) of this gene with the others. The pair-wise variation (V_n/V_n+1) was analyzed between the normalization factors NF_n and NF_n+1 by the <i>geNorm</i> software to determine the optimal number of references genes required for normalization. A threshold of V<0.15 was suggested for the valid normalization [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0120833#pone.0120833.ref001" target="_blank">1</a>]. B) Ranking of the 11 housekeeping genes based on the stability value (M).