cytoplasmic determinants and inductive signals contribute cell fate specification. Experimentally derived fate maps of embryos show that regions of the zygote or blastila develop into p older embryos The complete cell lineage has teen an revealing that programmed cell death cot ta to animal development in all species, the development potential of cells becomes progressively more limited as embryo ir development proceeds embryo receive and respond positional information that varies with location This information in the form of signaling molecules secreted by cells in spec regions of the embryo, such as the dorsal lip of the blastovoie the amphibian gastrula and the apical ectodermal ridge zone of polarizing activity of the vertebrate limb bud