Specification is defined as being somewhere on the path to being determined. To find out where cells are along this pathway, experiments are required. Determined cells continue to develop in accord with their prospective fate even when placed into a different region of the embryo. The basic characteristics of these three modes are summarized in Table 13. 2 in Gilbert. The mode of cell type specification is not determined by phylogenetic relationships.
Some invertebrates display autonomous specification, but other display conditional specification.
Arthropods display syncytial specification. Most chordates display conditional specification, but some display autonomous specification. Autonomous Specification of Cell Fate Example 1. Members of the Phylum Chordata, Subphylum Urochordata, Class Ascidia. The eggs of some ascidians have differentially colored cytoplasm.