Mitosis - Overview of Cell Cycle in Relation To Mitosis

Overview of Cell Cycle in Relation To Mitosis

The primary result of mitosis is the transferring of the parent cell's genome into two daughter cells. These two cells are identical and do not differ in any way from the original parent cell. The genome is composed of a number of chromosomes—complexes of tightly-coiled DNA that contain genetic information vital for proper cell function. Because each resultant daughter cell should be genetically identical to the parent cell, the parent cell must make a copy of each chromosome before mitosis. This occurs during the S phase of interphase, the period that precedes the mitotic phase in the cell cycle where preparation for mitosis occurs.

Each chromosome now has an identical copy of itself, and together the two are called sister chromatids. The sister chromatids are held together by a specialized region of the chromosome: a DNA sequence called the centromere.

The "real" process of mitosis begins when the chromosomes condense and become visible. In most eukaryotes, the nuclear membrane which segregates the DNA from the cytoplasm disintegrates into membrane vesicles. The nucleolus which make ribosomes in the cell also dissolves. The chromosomes align themselves in a line spanning the cell. Microtubules — essentially miniature strings— splay out from opposite ends of the cell and shorten, pulling apart the sister chromatids of each chromosome. As a matter of convention, each sister chromatid is now considered a chromosome, so they are renamed to daughter chromosomes. As the cell elongates, corresponding daughter chromosomes are pulled toward opposite ends. A new nuclear membrane forms around the separated daughter chromosomes.

As mitosis completes,the cell begins cytokinesis. In animal cells, the cell pinches inward where the imaginary line used to be (the area of the cell membrane that pinches to form the two daughter cells is called the cleavage furrow), separating the two developing nuclei. In plant cells, the daughter cells will construct a new dividing cell wall between each other. Eventually, the parent cell will be split in half, giving rise to two daughter cells, each with a replica of the original genome.

Prokaryotic cells undergo a process similar to mitosis called binary fission. However, the process of binary fission is very much different from the process of mitosis, because of the non-involvement of nuclear dynamics and lack of linear chromosomes.