Cell Cycle.
Early embryonic cells move through each phase of the cell cycle in a specific sequence. Conditions surrounding the embryo are so favorable that as quickly as a cell completes mitosis, it is ready to re-enter the cell cycle. Although these cells are under restriction point control (checkpoints), they do not spend a significant amount of time in G 0 . It appears that early embryonic cells continue to enter the cell cycle even when contacted on all surfaces by other cells. Thus, they do not exhibit density-dependent contact inhibition.