Final answer:
The First Growth Phase (G1) is a stage of the cell cycle where cells undergo growth, accumulate necessary components for DNA synthesis, and ensure sufficient energy reserves. A checkpoint here gauges readiness for DNA replication. If not ready, the cell enters a resting GO phase; otherwise, it progresses to the S phase.
Step-by-step explanation:
First Growth Phase (G1)
The First Growth Phase, also known as G1 or the first gap, is a crucial stage of the cell cycle during interphase. This phase is centered on cell growth and is characterized by the cell increasing in size. The G1 phase is essential for cells to perform their normal activities, such as accumulating the building blocks of chromosomal DNA and associated proteins, as well as ensuring sufficient energy reserves are available.
During this phase, there is also a checkpoint, termed the Cell Growth Checkpoint, which evaluates whether the cell is large enough and has synthesized the proper proteins for the subsequent S phase. If the cell is not ready to proceed, it may enter a resting period known as the GO phase.
Following G1, should the cell be prepared and pass the checkpoint, it then progresses to the S phase (Synthesis Phase), where DNA replication occurs. This preparation in the G1 phase ensures that the cell is well-equipped for the demands of DNA replication and subsequent cell division.