What is mitotic cell division
Cell Division - Meiosis and Mitosis
Table of Contents
• The cell division of mitosis
• The cell division of meiosis
Cell division of mitosis
There are altogether four Individual steps that serve to distribute the previously doubled DNA in equal proportions to both cells.
1. ProphaseIt is the first step in mitosis. The following steps take place here: Dissolution of the Nuclear membrane, Disappearance of the Nucleolus (Nuclear bodies = compressed DNA) and the formation of the spindle apparatus for the later division of the Chromosomes.
2. metaphaseThe DNA condenses into the so-called Chromatin, which is made up of DNA itself and histones, proteins that DNA is wrapped around. This chromatin is clearly visible with the light microscope and can be extracted from the cells in special experiments detached become. At the same time, the chromatin is arranged in the so-called equatorial plate in the middle of the cell, which can be seen as a darker stripe in the microscope. In the metaphase, each centromere of the chromosomes is connected to the spindle apparatus in such a way that the centromere is connected to both of them through the spindle apparatus Cell poles Has contact.
3. AnaphaseThis is where the division of the chromosms takes place: Through the Spindle apparatus the chromosomes are separated at the centromere and pulled to the corresponding pole.
4. TelophaseOnce the simple set of chromosms has arrived at the cell poles, the two newly formed cells, the Nuclear envelope is newly formed and the nucleolus is visible again.
The cell division of meiosis
Shortly before the start of meiosis, one takes place in the sperm and egg cells Doubling instead of DNA, which results in both egg cells and sperm having a double diploid set of chromosomes. In meiosis, the diploid set of chromosomes becomes two haploid through division into two cells.
Meiosis can also be incorporated into the four Subdivide phases pro, meta, ana and telophase, but this first meiosis is followed by a second:
1. ProphaseIt clearly lasts longer than with mitosis. What is characteristic here is that there is a so-called "Crossing over" can occur, i.e. maternal and paternal chromosomes attach to each other, which leads to an exchange of chromosomes, which is one of the causes of genetic diversity.
2. metaphasesee above.
3. AnaphaseHere the diploid is divided into two haploid chromosome sets by the spindle apparatus pulling the chromosomes apart on the centromere. How paternal and maternal chromosomes are distributed coincidentally.
4. Telophasesee above.
Meiosis is followed by the second meiotic division, which proceeds like mitosis, consequently four cells with a haploid set of chromosomes have arisen after this second meiotic division.
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