Mitosis

What is Mitosis?

Mitosis is a nuclear division followed by cytokinesis, and produces two identical daughter cells during interphase, prophase, metaphase, anaphase, and telophase. The phases mentioned above are summarized in the following table:


Table 1: The phases of Mitosis

Image	Phase	Description
	Interphase	This is the period prior to the replication of DNA. In this phase, the cell increases in mass in preparation for cell division. The cell is still performing its regular activities in this phase. Chromosomes are not clearly seen in the nucleus, although a dark spot called the nucleolus may start becoming visible. This is also the phase where DNA replication occurs.
	Prophase	Chromatin in the nucleus begins to condense and becomes visible under the microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibres extend from the centromeres. The mitotic spindle forms. Part 2 (Prometaphase) The nuclear envelope breaks down, so that the spindle microtubules and the chromosomes are no longer separated by a membrane boundary. The microtubules begin to interact with the chromosomes, and the chromosomes start moving to with their centromeres to the middle of the spindle, at a site known as the metaphase plate.
	Metaphase	Spindle fibers align the replicated chromosomes along the middle of the cell nucleus (metaphase plate). On either side of each centromere are sites for microtubule attachment to the chromosome. This is done in order to ensure that in the next phase, when the chromosomes are separated, each nucleus will receive one copy of each chromosome. With each replicated chromosome giving rise to two daughter chromosomes.
	Anaphase	The paired chromosomes (sister chromatids) separate and begin moving to opposite ends (poles) of the cell. Spindle fibers that are not connected to any chromatids lengthen and elongate the cell. At the end of anaphase, each pole contains a complete set of chromosomes. In this stage the cell is almost ready to split into two.
	Telophase	Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes separate and are no longer visible under the microscope. The spindle fibers dissolve, and the cell begins its division into two new cells. Cytokinesis also starts during this phase.
Very similar to the anaphase,  besides the nuclei which are  already formed in cytokinesis.	Cytokinesis*	Cytokinesis results in pinching the cell into two daughter cells, each with one nucleus. After this phase there are two distinct cells, each contains the same DNA, which was formed during the mitosis process.
	Interphase*	There are two new, fully functioning cells at this point, which contain the exact same DNA. These two cells will eventually undergo mitosis again to create more cells, as instructed by the DNA in our nucleus.

*Not part of the mitosis cycle but are included to provide a better explanation of mitosis and considered as a part of cell division.


Pictures from: http://tainano.com/chin/Molecular%20Biology%20Glossary.htm



Conclusion

Each living organism must undergo mitosis in order to preserve its DNA and develop. This process is what allows us and every other organism to fully function, but how is DNA replication really works? And how can it possibly create an identical copy of itself without any errors? Make sure you read the next page for answers to these questions.


Work Cited: http://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html
                  http://www.life.umd.edu/CBMG/faculty/wolniak/wolniakmitosis.html