During interphase, the cell carries out all the normal processes of cell growth and prepares for cell division. For a cell to proceed from interphase into the mitotic phase of the cell cycle, many internal and external conditions must be satisfied. Three stages comprise interphase: G1, S, and G2.  

G1 Phase (First Gap) 

The first stage of interphase is called the G1 phase (first gap) because little change is visible. During this time the cell grows and accumulates the building blocks of chromosomal DNA and the associated proteins as well as creating sufficient energy to create new chromosomes and DNA.

G1 Checkpoint: This is a very important regulatory point within the cell cycle, which helps in proper cell division and maintenance. There are several stages in the cell cycle, and the first gap phase, G1, forms a very important stage that leads to DNA synthesis (S phase) and further cell division (M phase). Check if the DNA is damaged and restricts it from coming through if it does.

G0 Checkpoint: The G0 phase is a important phase in the cell cycle where cells leave the normal cell cycle to either temporarily or permanently stop actively dividing. If it notices damage then the cell will try to fix this damage if it cannot do this then it will permanently stop the cell from dividing. Although G0 is often regarded as a part of the G1 phase, it is a different phase since cells in G0 are not actively preparing for DNA replication or cell division. Instead, they are in a state of metabolic maintenance, and their movement through the cell cycle is arrested.   

S Phase (Synthesis of DNA)  

The synthesis phase of interphase is the longest phase of the cell cycle because the genetic material is being duplicated.

During the interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase DNA replication yields identical pairs of DNA molecules called sister chromatids, these are attached to the centromeric region. During the S phase the centrosome is duplicated. The two centrosomes will bind to the mitotic spindle which moves the movement of chromosomes during mitosis. Centrioles are located at the center of each animal cell the centrosomes of animal cells are associated with a pair of rods, the centrioles. Centrioles help organize cell division. Centrioles are not present in the centrosomes of other eukaryotic species, such as plants and most fungi. 

G2 Phase (Second Gap) 

In the G2 phase, the cell replenishes its energy stores and makes proteins needed for chromosome manipulation. This causes some cell organelles to be duplicated and then the cytoskeleton is dismantled to provide additional building blocks for the mitotic phase. Cell growth may continue during G2. Any final steps for the mitotic phase must occur before the cell is able to enter the first stage of mitosis. Therefore going into the G2 checkpoint to make sure the cell can proceed.

G2 Checkpoint: Controls and ensures that dividing cells are correctly prepared to enter mitosis or the M phase of the cell cycle. This checkpoint occurs during the G2 phase after DNA replication but before the cell has started to divide, ensuring that DNA replication is complete. The G2 checkpoint also has the function of delaying or stopping the cell cycle in case of errors detected during DNA replication or damage to the DNA, then it gives the cell time to fix the damage.

Mitosis phase (M)

This is the last phase of the cycle where two daughter cells are formed. Each daughter cell has all the materials to start this process again due to the formation and replication of new DNA and chromosomes.

The nucleolus turns into the shape of a rounded body within the nucleus and then shrinks and disappears. It occurs with the disappearance of the nuclear membrane. 

The end of the prophase is marked by the beginning of the organization of a group of microtubules to form a spindle. In later stages of mitosis, the chromatids will attach to this spindle and pull apart, ensuring that each daughter cell has an identical and complete set of chromosomes.

The pulling by the kinetochore fibers against the poles places tension on the cohesin complex at the kinetochores this signals that the sister chromatids are properly bioriented. 

The cell continually monitors the microtubule attachments to the chromosomes, and the tension produced by microtubules pulling on the kinetochores serves to properly align the sister chromatids at the metaphase plate .