Figure 8

Graphic analysis of TAP and RAP [29]. A schematic representation of AT skews at the third position of codon, A₃/(A₃+T₃), plotted against GC skews at the third position of codon, G₃/(G₃+C₃), for all CDS in a genome. The circles represent those CDS on the lagging strands (usually smaller numbers) and the leading strand (usually larger numbers). Line B _II connecting the average points, (x₂, y₂) and (x₁, y₁), of these two populations represents the average distance between the populations. (A) Scenario I – presence of RAP only (no TAP). No TAP is present. RAP creates G and T excess in the leading strand (and A and T excess in the lagging strands), thus separating the two populations in the indicated direction. The relative strength of RAP corresponds to the length of line $B_1=\sqrt{{(x_2-x_1)}^2+{(y_2-y_1)}^2}$. Line B _I (double arrows) intercepts the midpoint (0.5, 0.5). (B) Scenario II – presence of both RAP and TAP. TAP exerts asymmetric effect on CDSs on both the leading and lagging strands, thus pushing B _I away from the midpoint (0.5, 0.5). The relative strength of TAP corresponds to B _II (arrow), the distance between B _I and the midpoint. Modified from Lobry and Sueoka [29].