Fig. 4.
Sensitivity of positive feedback to receptor levels and binding parameters. (a) tkv zygotic mutant embryo homozygous for the tkv7−/− allele exhibits WT pMad staining. (b) Robustness to specific level of receptors. The number of cells from the DM whose level of BR exceeds a threshold level of 50% of the reference system maximum 60 min. (○) and steady-state (●) is shown for receptor levels that vary from 16 nM to 1.6 × 105 nM. (c and d). Patterning is more sensitive to the on-rate (c) and off-rate (d) of BMP binding to receptor. (e) For proper patterning, the on-rate for SBP binding BMP is ≈6-fold greater than the on-rate for BMP binding receptor. (f) Patterning is essentially independent of the specific size of the embryo over a wide range of lengths.