Definition: Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.
Input: Abstract: 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.

A molecular gradient in early Drosophila embryos and its role in specifying the body pattern.