Compare and Contrast Mitosis and Meiosis
Cell division is the basis of life itself. It is how humans and animals grow and reproduce. When cells divide, two or four daughter cells are produced from one mother cell. Cellular division has three main functions: reproduction of an entire unicellular organism, formation of gametes, eggs and sperm, for sexual reproduction in humans and animals, and growth and repair of tissues in humans and animals. The process of meiosis forms gametes and the process of mitosis produces the other cells. Compare and Contrast Mitosis and Meiosis Mitosis and meiosis are two types of cells division.
Mitosis is cell division that results in the duplication of cells; the daughter cells genetic copies of the parent cell. This cell multiplication allows for replacement of old cells, tissue repair, growth and development. Mitosis is how the cells of our body make more cells for growth, development and repair. Meiosis is how our body makes sex cells, or gametes (eggs or sperm). Before a cell can enter cell division, it needs to prepare itself by replicating its genetic information and all of the organelles. All of the preparations are done during the interphase.
Interphase proceeds in three stages, G1, S, and G2. Cell division operates in a cycle. Therefore, interphase is preceded by the previous cycle of mitosis or meiosis and cytokinesis. Mitosis is composed of interphase, prophase, metaphase, anaphase and telophase. Prophase is characterized by the condensation of chromosomes consisting of two chromatids, disappearance of the nucleolus and nuclear membrane, and formation of the mitotic spindle. In metaphase, the stage of cell division in which the duplicated chromosomes become aligned along the center of the cell, called the equatorial plate or metaphase plate.
They are now ready to be pulled to the two poles by spindle. Anaphase begins when the duplicated centromeres of each pair of sister chromatids separate, and the now-daughter chromosomes begin moving toward opposite poles of the cell due to the action of the spindle. At the end of anaphase, a complete set of chromosomes has assembled at each pole of the cell. The final phase of cell division is telophase. In this stage membranes form around the two groups of chromosomes each at opposite ends of the cell to produce the two nuclei of the daughter cells.
The spindle disappears, and the cytoplasm usually divides (in the process called cytokinesis). In mitosis, telophase is preceded by anaphase (Marieb 101-103 pp). Like mitosis which is the process in cell division by which the nucleus divides, in stages of interphase, prophase, metaphase, anaphase, and telophase, and resulting in two new daughter cells, meiosis also goes through these same stages. Meiosis also differs from mitosis in several major ways. After completing interphase, prophase, metaphase, anaphase, and telophase meiosis starts a new cycle. The beginning of the new cycle is telophase I.
Telophase I in this phase, like in mitosis the chromosomes are moved into opposite poles and the nuclear envelope reforms and the spindle is broken down. Remember that there are two chromosomes, not one as in mitosis. The pairs of chromosomes then separate and move to opposite ends of the cell, and the cell itself divides into two cells. In meiosis the cell goes directly from telophase I to prophase II. In prophase II the nuclear envelope is dissolved and the spindle is again. Prophase II is identical to prophase of mitosis except that there is half the amount of chromosomes.
In metaphase II, the stage of cell division in which the duplicated chromosomes become aligned along the center of the cell, called the equatorial plate or metaphase plate. They are now ready to be pulled to the two poles by spindle. Next there is anaphase II. Here the non replicated chromosomes move to the poles. The kinetochores move towards the poles, splitting up the sister chromatids. The last stage, telophase II, the chromatids concentrate in the poles and the nuclear envelope is reformed and the spindle again is dissolved.
The cells divide for the last time, leaving a total of four haploid cells, which have half the chromosomes of a diploid cell. Unlike the daughter cells from mitosis, the daughter cells produced here cannot immediately cycle back to interphase(Marieb 1071 -1074 pp). Meiosis is different than mitosis in terms of the cell division number. During mitosis, chromosomes are duplicated once, and cell divides once, therefore each daughter cell has equal chromosome number which is also equal to the mother cell.
During meiosis, chromosomes are also duplicated, cell division occurs twice consecutively, leading the half of the chromosome number in 4 daughter cells. This process is used for generating germ line cells, the gametes. When gametes from male and female parents meet, they form normal diploid chromosome number again. http://kvhs. nbed. nb. ca/gallant/biology/mitosis_meiosis. html References http://kvhs. nbed. nb. ca/gallant/biology/mitosis_meiosis. html Marieb, Elaine Nicpon. (2004). Human Anatomy & Physiology (6th edition). San Francisco, CASample Essay of PapersOwl.com