Why is g1 phase important

We will begin our discussion of the events that take place during interphase with those that occur immediately after a cell has successfully divided during mitosis.

This phase is called G1. G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA replication during S phase. During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the centrosomes undergo replication. Before a cell begins DNA replication, it must ensure that it is biologically ready to take on such a process.

G1 is the phase when this cellular monitoring takes place. During G1, the cell reviews the cellular environment and the cell size to ensure that the conditions are appropriate to support DNA replication.

Not until the cell is ready does it leave G1. If all is not ready to undergo DNA replication, cells can pause during G1 and enter a phase called G0. Depending on a cell's preparedness to continue in the cell cycle, G0 can last days, weeks, or even years. When the cell has reached an appropriate size and is in a supportive environment for DNA replication, it will exit either G1 or G0 and enter the next phase of interphase called S phase.

S phase, or synthesis, is the phase of the cell cycle when DNA packaged into chromosomes is replicated. This event is an essential aspect of the cell cycle because replication allows for each cell created by cell division to have the same genetic make-up. During S phase a number of events additional to chromosomee replication take place. Cell growth continues through S phase, as does the rate of synthesis of a number of proteins and enzymes that are involved in DNA synthesis.

Once DNA replication is complete the cell contains twice its normal number of chromosomes and becomes ready to enter the phase called G2. The M, G1, G2 and S phases are the four stages of the cell cycle; all stages besides M are said to be a part of the overall interphase process. Interphase is the process by which cells accumulate nutrients, grow and divide. The G1 phase is often referred to as the growth phase, because this is the time in which a cell grows. During this phase, the cell synthesizes various enzymes and nutrients that are needed later on for DNA replication and cell division.

The duration of the G1 phase is variable and it often depends on the nutrients that are available to a cell. The G1 phase is also when cells produce the most proteins. Every cell has certain regulators that help monitor the growth in the cell.

At the end of the G1 phase, cells have a "restriction point," which is a safeguard that ensures that protein synthesis occurred properly and the cell's DNA is intact and ready for the future stages. The specific safeguards are proteins with the name, cyclin-dependent kinases or CDK ; they also initiate DNA division during the S phase of the cell cycle.

Although G1 is a phase of the cell cycle, it also has four subphases that describe its processes and functions. The four stages are competence, entry, progression and assembly. Competence refers to the process by which a cell absorbs nutrients and things from outside of the cell membrane. As these materials enter the cell in the entry subphase, they are used to help the cell grow, which takes place during the progression subphase.