How morphogen gradients can give rise to developmental patterns.
(A) Schematic diagram of the concentration of a given morphogen (purple) as the distance from the source-cells (blue) increases. This can lead to morphological boundaries formed by different transcriptional programs, corresponding to the thresholds of morphogen-receptor activation. (B) A close up of the movement of the morphogen across a field of ‘sink-cells’ which can take-up the morphogen.