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Figure 8 | BMC Genomics

Figure 8

From: Quantitative analysis of mutation and selection pressures on base composition skews in bacterial chromosomes

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 = ( x 2 x 1 ) 2 + ( y 2 y 1 ) 2 MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGcbGqdaWgaaWcbaGaeGymaedabeaakiabg2da9maakaaabaGaeiikaGIaemiEaG3aaSbaaSqaaiabikdaYaqabaGccqGHsislcqWG4baEdaWgaaWcbaGaeGymaedabeaakiabcMcaPmaaCaaaleqabaGaeGOmaidaaOGaey4kaSIaeiikaGIaemyEaK3aaSbaaSqaaiabikdaYaqabaGccqGHsislcqWG5bqEdaWgaaWcbaGaeGymaedabeaakiabcMcaPmaaCaaaleqabaGaeGOmaidaaaqabaaaaa@42E1@ . 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].

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