MacDonald, P.M., Struhl, G. (1986). A molecular gradient in early Drosophila embryos and its role in specifying the body pattern.  Nature 324(): 537--545.

FBrf0045103

Research paper

After fertilization, the protein products of the Drosophila homeobox gene caudal (cad) accumulate in a concentration gradient spanning the anteroposterior axis of the developing embryo. Mutations in the cad gene that reduce or eliminate the gradient cause abnormal zygotic expression of at least one segmentation gene (fushi tarazu) and alter the global body pattern.