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Introduction to Mitosis

In this section, we will review the events that constitute mitosis, or M phase. Recall that mitosis occurs in somatic cells as opposed to germ cells, which undergo meiosis. Mitosis follows G2, and is the time in which cells separate their duplicated contents and divide. Division of cells at the end of mitosis yield identical diploid cells.

Though cell division is the defining characteristic of mitosis, a number of events must take place during mitosis before the cell is ready to split. We will review the essential cellular events that take place during mitosis in order to gain an understanding of how the cell cycle ultimately yields new cells.

Mitosis involves a five step process, and then a final, culminating sixth step, called cytokinesis. The five steps of mitosis and cytokinesis are often considered to be two distinct sub-phases within the general cell-cycle phase we've been calling mitosis, or M phase. For ease of reference, we will use the term M phase through the rest of this SparkNote to refer to the combination of the five steps of mitosis and cytokinesis.

The five steps of mitosis, called prophase, prometaphase, metaphase, anaphase, and telophase, constitute the period in which the cell makes preparations for cell division. The five phases are differentiated by specific events of preparation for cell division. Cytokinesis refers to the actual cleavage event, splitting the cell in two.

In this SparkNote on mitosis we will review the nearly universal cellular characteristics of the five stages of mitosis and of cytokinesis. Our discussion will be guided by the order in which events take place. We'll begin at the end of interphase in G2 and go through mitosis and cytokinesis, ending where the resulting cells re-enter interphase at G1.