The mid-blastula transition is characterized by a switch to longer cell cycles and increased embryonic transcription. Gastrulation is the process by which presumptive endoderm and mesoderm are internalized. This involves active and coordinated cell movements. Distinct types of cell movements are employed during gastrulation. The egg and early embryo may contain localized cytoplasmic determinants.
Cleavage proceeds gastrulation.
The cleavage pattern of the embryo is influenced by the amount of yolk in the egg. You will learn that as gastrulation proceeds, the avian and mammalian embryos look very similar. The dramatic upregulation of embryonic transcription 2. The lengthening of the cell cycle. The egg is filled with things needed to start embryogenesis, including regulatory factors.