Figure 3

Matches to our σ^Aweight matrix WM1 exhibit a clear positional bias. Histograms of positions of the matches to our σ^Aweight matrix WM1 between (a) divergent and (b) convergent operons. In (a), positions are measured relative to translation start. In (b), positions are measured relative to the downstream end of the region. In either case, the first upstream base is assigned the position -1. The expected distribution, under the null hypothesis that the matches are uniformly distributed in their upstream regions, is denoted by *. Probability P of the observed distribution under the null hypothesis is reported as the significance score -log₁₀P.