Cell division is the process of the formation of two or more daughter cells from the parent cell. Typically, cell division is part of a larger cell cycle . [1] Eukaryotes have two different types of cell division: vegetative division, in which each daughter cell is genetically identical to the parent cell ( mitosis ) [2] and reproductive cell division, in which the number of chromosomes in the daughter cell is halved to produce gametes ( meiosis )
Content
Prokaryotic Cell Division
Prokaryotic cells divide in two. First, the cell lengthens. It forms a transverse septum. Then the daughter cells diverge.
Eukaryotic Cell Division
There are two ways of dividing the nucleus of eukaryotic cells: mitosis and meiosis .
Amitosis
Amitosis, or direct fission, is the division of an interphase nucleus by constriction without the formation of a fission spindle. This division is found in unicellular organisms. Amitosis, in contrast to mitosis, is the most economical way of dividing, since the energy costs are very small. Cell division in prokaryotes is close to amitosis. A bacterial cell contains only one, most often a circular DNA molecule, attached to the cell membrane. Before cell division, DNA is replicated and two identical DNA molecules are formed, each of which is also attached to the cell membrane. During cell division, the cell membrane grows between these two DNA molecules, so that ultimately in each daughter cell there is one identical DNA molecule. This process is called direct binary division.
Division Preparation
Eukaryotic organisms consisting of cells having nuclei begin to prepare for division at a certain stage of the cell cycle, in interphase. It is during the interphase period in the cell that the process of protein biosynthesis takes place, all the most important cell structures are doubled. Along the original chromosome from the chemical compounds present in the cell, its exact copy is synthesized, the DNA molecule is doubled. Doubled chromosome consists of two half-chromatids. Each chromatid contains one DNA molecule. Interphase in the cells of plants and animals lasts an average of 10-20 hours. Then comes the process of cell division - mitosis.
Mitosis
Mitosis - (less commonly: karyokinesis or indirect division ) - division of the nucleus of a eukaryotic cell while maintaining the number of chromosomes . Unlike meiosis , mitotic division proceeds without complications in cells of any ploidy , since it does not include, as a necessary step, conjugation , chromosomes in prophase.
Meiosis
Meiosis is a special way of cell division, which results in a halving of the number of chromosomes in each daughter cell. It was first described by W. Fleming in 1882 in animals and E. Strasburger in 1888 in plants. With the help of meiosis, gametes are formed. As a result of reduction, spores and germ cells of the chromosome set receive, in each haploid spore and gamete, one chromosome from each pair of chromosomes present in this diploid cell. In the course of the further process of fertilization (gamete fusion), the new generation organism will again receive a diploid set of chromosomes, that is, the karyotype of the organisms of this species remains constant among generations.
Cell division
In the process of dividing the body of a eukaryotic cell ( cytokinesis ), the separation of the cytoplasm and organelles between new and old cells occurs.
See also
- Cytology
Notes
- β Oxford Dictionary of Biology / Robert.S Hine. - 6th. - New York: Oxford University Press, 2008 .-- P. 113. - ISBN 978-0-19-920462-5 .
- β Griffiths, Anthony JF Introduction to Genetic Analysis. - 10. - New York: WH Freeman and Company, 2012. - P. 35. - ISBN 978-1-4292-2943-2 .