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.
