Driever, W., Thoma, G., Nusslein-Volhard, C. (1989). Determination of spatial domains of zygotic gene expression in the Drosophila embryo by the affinity of binding sites for the bicoid morphogen.  Nature 340(6232): 363--367.

FBrf0050639

Research paper

The maternal gene bicoid is a key component of the system that determines the pattern of the anterior half of Drosophila embryos. The bicoid protein forms a concentration gradient in early embryos, and is known to bind DNA. Specific binding sites are now shown to confer expression in a region of the embryo that depends on their affinity for bicoid protein: sites of high affinity allow expression further down the bicoid protein gradient than sites of low affinity.