Division of the cytoplasm is known as cytokinesis . Once new cells are formed by the division of an older cell, the new cells pass through a predictable series of events. The cells mature , and as they do so, they grow larger and either become specialized to serve a particular function, or they themselves divide to produce yet another generation of cells. The various events of nuclear division, cytoplasmic division, cell growth, and cell maturation are repeated in each generation of cells. The period of time and the sequence of events from one cell division to the next cell division is collectively referred to as the cell cycle .
Mitosis occupies only a relatively small part of the cell cycle.
There is a rather long time interval, known as interphase , between the end of one mitotic division and the beginning of the next. During this DNA duplication, the DNA of each chromosome splits in half lengthwise. DNA synthesis produces a new half for each half of the DNA molecules. The result is two exact copies of the DNA of every chromosome. These two copies stick together along their length, and together with their proteins form the two chromatids of each chromosome .