Describe the main events in each stage of a cell cycle. G1
The correct answer and explanation is:
The G1 phase, or Gap 1 phase, is the first stage of interphase in the cell cycle. It follows the completion of cell division (mitosis) and is primarily focused on cell growth, preparation for DNA replication, and ensuring that the cell is ready for the next phase.
During G1, the cell undergoes significant growth, increasing its size and producing the necessary proteins, enzymes, and organelles for cellular function. It also carries out its normal metabolic activities. The cell synthesizes RNA, proteins, and other molecules required for the replication of DNA in the subsequent phase, S-phase.
A crucial event in G1 is the checkpoint known as the “G1/S checkpoint.” At this stage, the cell assesses whether it is suitable for DNA replication. If the cell is damaged or not ready, it can enter a resting state called the G0 phase, where it remains inactive until it is ready to proceed. If everything is in order, the cell progresses into the S phase, where DNA replication occurs.
The G1 phase also includes preparation for the synthesis of specific proteins and the activation of regulatory molecules. Cyclins, along with cyclin-dependent kinases (CDKs), help control the progression of the cell cycle. Cyclin D, for example, plays a key role in the transition from G1 to S.
The duration of G1 varies depending on the type of cell and environmental factors, such as nutrient availability and external signals. In rapidly dividing cells, G1 may be brief, while in other cells, it may take longer.
In summary, the G1 phase is crucial for cellular growth and preparation for DNA replication. It ensures that the cell is healthy and ready to enter the S-phase of the cell cycle.