Fig. 3.

Positional cues for Kr. (A) Summary of three different dual-regulation models (see also Fig. 1A). (B and C) Positional cue test. Computer simulations were done to examine the consequences of changing the positions of the Kr expression pattern along the AP axis. In most cases, both the solution quality (B) and the number of good solutions (C) are maximal when Kr is located in its normal position (see Methods). None of the dual-regulation solutions match the endogenous Kni expression pattern (see the gray arrows). Thus, dual regulation by Hb can explain the Kr pattern, but not Kni expression.