Interphase, or the period of cell growth, comprises most of the cell cycle. The majority of cells spend around 90 percent of their lives in this phase. Cells that do not undergo the division process perform the activities associated with interphase for their entire lives. Interphase can be divided further into three parts called G1, S and G2. The first phase, G1, is after the cell has been formed but before it begins to make its own DNA. Cells in G1 carry out protein synthesis and other common cellular functions. During the S stage, the cell replicates and synthesizes its DNA. The stage is complete when there are two basic blueprints of the cell's genetic material. In the last sub-stage, G2, the cell carries on normal protein synthesis and cellular functioning before it begins to divide.
Prophase is the first step in the total cell division process, which is called mitosis. In this stage, the copied chromosomal material begins to condense into individual chromosomes. A spindle, which will perform the mechanics of the division process, forms in the cytoplasm of a cell, completing the prophase stage. Before prophase ends, two distinct, physical copies of the cell's genetic material are present.
The next stage in cell division, metaphase, begins when the chromosomes line up across the middle of the cell's interior along a line called the metaphase plate. This process is seen in conjunction with the dissolution of the cell's original nucleus, which is replaced by the chromosomes along the metaphase plate.
Anaphase is distinguished by the splitting of the chromosomes into individual chromatids. The spindle, formed during prophase, by way of its center, called a centromere, pulls the chromosomes apart toward opposing ends of the cell. In healthy cell division, a complete set of genetic information is present at both ends.
The final stage in cell division, telophase, is when the cell undergoes complete physical differentiation. The cytoplasm of the cell divides completely, a process called cytokinesis. At this point, the chromosomes begin to decondense in order to function effectively, and a separate nuclear membrane forms around the material. The daughter and reformed parent cell enter the cell growth stage, G1, and the cycle begins anew.