1. Cell Growth:
* The cell increases in size.
* It produces new organelles (e.g., mitochondria, ribosomes, endoplasmic reticulum).
* It synthesizes proteins and enzymes needed for future stages.
2. Metabolic Activity:
* The cell is highly metabolically active, engaging in normal cellular functions.
* This includes processes like protein synthesis, energy production, and waste removal.
3. Checkpoint Control:
* The G1 checkpoint, also known as the restriction point, is a critical control mechanism.
* It assesses whether conditions are favorable for DNA replication.
* Factors like nutrient availability, cell size, and the presence of growth factors are evaluated.
* If the conditions aren't met, the cell can enter a quiescent state (G0) or undergo programmed cell death (apoptosis).
4. Preparation for DNA Replication:
* The cell starts accumulating the necessary proteins and enzymes for DNA replication.
* These include DNA polymerase, helicase, and other replication machinery components.
* The cell also begins to replicate its centrosomes, structures that will play a role in cell division.
5. Duration:
* G1 can vary significantly in length depending on the cell type and external factors.
* It can be short (a few hours) or long (several days).
Overall, G1 is a critical period for cell growth, metabolic activity, and preparation for the next stage of the cell cycle, the S phase where DNA replication occurs.
