Clonal analysis can be used to assess the degree of cell determination. The determined state of cells is always never reversible. Morphogenetic Movements a. Delamination is the splitting of one cell layer into two parallel layers. Epiboly is the spreading movement of an epithelial layer over a deeper cell layer. Invagination is the local inward buckling of an epithelium.
Involution is the migration of single cells from an epithelial layer into an embryonic cavity.
Localized Cytoplasmic Determinants a. The polar lobe of mollusks shunts vegetal cytoplasm into the D cell lineage. Bicoid mRNA serves as a muscle determinant in Drosophila. The polar granules of insects are located at the anterior egg pole. The yellow myoplasm of ascidians acts as a germ cell determinant.