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MITOSIS REVIEW
What is mitosis and why do cells undergo this process?
Mitosis is a process where a single cell divides to 2 identical daughter cells for many reasons .Cells
usually undergoes mitosis because of many important reasons. For example, cells need to go undergo
mitosis to replace or repair old cells that may have been damaged. Another reason is they need mitosis
during cell replication for cell growth. The purpose of mitosis is cell regeneration, growth, and asexual
reproduction. Mitosis is a single nuclear division that results in two nuclei that are usually partitioned into
two new daughter cells.
STAGES OF MITOSIS:
Interphase: Cells spend 90% of the cycle on this stage.
During interphase, the cell grows and makes a copy of its DNA. It is then followed by the G1, S and G2
Stage, which is part of the interphase.
During the G1 phase in the cell cycle, also called the first gap phase, the cell grows larger and makes
more of its ribosome’s, organelles, and proteins. It continues to do its job that the cell needs to do.
The cell moves from G1 into a phase called S phase. During this phase, it synthesizes a complete copy of
the DNA chromosomes in its nucleus.
In the G2 phase the cell grows more, makes additional proteins and organelles, and begins to reorganize
its contents in preparation for mitosis. G2 phase ends when mitosis begins.
Other types of cells, however, divide slowly or not at all. In these cases, the cells may exit the G1 phase
and enter a resting state called G0. In G0a cell is not actively dividing or preparing to and is just carrying
out its job. There are 3 major checkpoints for the cell to know if it can start mitosis known as G1, G2 and
M phase. G1 is the most important because if it receives the signal to start the cell cycle or not.
PROPHASE
In this stage the chromosomes become visible and the centrioles separate and move to opposite poles of
the cell.
PROMETAPHASE:
A stage in between prophase and metaphase.
This is the stage where the spindle fibers will attach to the centromeres. Microtubules will attach to the
kinetochores on the centromere. Chromosomes slowly begin to start moving.
METAPHASE:
In this stage the chromosomes line up across the center of the cell and become connected to the spindle
fibers at their centromeres. Spindle fibers will be used to help the chromosomes move.
ANAPHASE:
The third stage of mitosis. In this stage the sister chromatids separate into individual chromosomes and
are pulled apart by motorproteins. At the end of this stage, both ends have equal and completed sets of
chromosomes.
TELOPHASE:
During this stage the chromosomes gather at opposite ends of the cell and lose their distinct rod like
shapes. Two new nuclear membranes then form around each of the two regions of DNA and the spindle
fibers disappear.
CYTOKINESIS:
The process that follows the last stage of mitosis. With two complete copies of the DNA now in two
different regions of one cell, the cell membrane will pinch and divide the cytoplasm in half. This is done
by the occurrence of a cleavage furrow. The result is two individual cells that are identical to the original
cell. Each of the two new cells has a complete copy of the DNA and contains all of the organelles that the
original cell had. In plant cells, a cell plate separates the cytoplasm. Both cells will have 46 chromosomes
at the end.
There can also be errors in mitosis. Most of the time it will be fixed. Changes in somatic cells will only
happen to you and won’t be passed down. If it doesn’t get repaired, apoptosis can happen where the cells
die. It can also lead to genetic disorders.