Final answer:
Rapidly dividing embryonic cells shorten S-phase duration by increasing the number of origins of replication to accommodate the fast pace of cell division. The cell cycle is regulated by both internal and external factors, with proteins and growth factors playing a crucial role in its progression.
Step-by-step explanation:
Rapidly dividing embryonic cells shorten S-phase duration by increasing the number of origins of replication. DNA replication occurs during the S phase, and in the case of embryos or rapidly dividing cells, this process must be much quicker to match the fast pace of cell division.
In typically dividing cells, each cell cycle, including G₁, S, G₂, and M phases, can range from approximately 16 to 24 hours, whereas in early embryonic stages or in cells like fertilized eggs of fruit flies, the entire cell cycle can be completed in just minutes.
To facilitate such rapid division, cells undergo a shortened cell cycle. The stages of the cell cycle are carefully regulated; for instance, events external to the cell such as the release of growth-promoting hormones or cell crowding can influence the initiation or inhibition of cell division.
Internally, proteins such as cohesins and tubulins are synthesized in preparation for cell division, while tumor suppressor genes and oncogenes may play a role in abnormal cell division leading to cancer.
In the context of embryogenesis, the mechanics that allow for an abbreviated S phase are essential to understanding both normal growth and the potential for aberrations that can lead to disease.
The fast pace of embryonic cell division necessitates a rapid and efficient DNA replication process, pivotal to successful development.