The nonlinear curve of hb border response to Bcd variation in (A) the simplified and (B-E) full models. (A): The value of Bcd concentration at the A-P position where the initial Hb profile intersects the corresponding basin boundary from Fig. 5C versus this position, for all but one Bcd profiles from the ensemble (Bcd profile #54 was excluded from the analysis as explained in the text). The colors mark the three solution clusters I-III from Fig. 2: green corresponds to class I, blue to II, and red to III. The yellow stars indicates the median Bcd case. The inset in (A) shows the Bcd dependence of the attraction basin boundary for the attractor A3 at fixed A-P position equal to 47% EL. As explained in Methods, the attraction basin has the form of interval (c1,c2) at the Hb axis; the Bcd concentration at 47% EL versus the value [Hb] = c2 at the same position is plotted in the inset for all Bcd profiles from the first family. (B): The same response curve as in (A) but obtained from calculations in the full model (1) and with the hb border positions used instead of the intersection point positions. The inset shows all Bcd profiles used in the calculations. Colors in (B) correspond to those in (A). (C): The response curve expressed in terms of 'masses' of the Bcd patterns and Hb solutions. The mass is calculated as the integral of a pattern (a Bcd profile or a Hb solution at the end of cleavage cycle 14A) over the spatial region 35-64%EL. The Hb pattern mass positively correlates with the hb border position (data not shown). The dots represent results of calculations in the full model, while the triangles correspond to calculations with the same equations but with the gap gene cross regulation of hb turned off (Thb←aset to zero in (1) for each gap gene a). The green, blue, and red symbols indicate cases with a small, intermediate, and large mass of the Bcd patterns, respectively. The Bcd and Hb patterns used in calculations of the colored dots are shown in (D) with respective colors, and the same for triangles in (E). The Bcd patterns are dashed lines, and the Hb solutions are solid ones.