Senin, 24 Mei 2010

Stages of cell division


Inter phase. At the stage of inter phase, the cell is considered a rest from division process. However, the actual stage of the inter phase is an active and important step to prepare the division. Preparation of DNA replication (doubling the DNA from one copy into two copies). In general, most of the time the cells are alive at this point. Further inter phase subdivided into gap-1 phase, synthesis phase, and phase-second gap.

Pro phase. At the pro phase stage, DNA began packaged or packaged into chromosomes. Chromosome is the densest structure of DNA packaging. Necessary DNA packaged into chromosomes. In early pro phase, the chromosomes began to appear under the microscope. Because at this stage, has been preceded by chromosomal DNA replication (two chromatids: 2c, two chromosomes: 2n), then the chromosome was composed of the twin chromatids are linked at the centromere. The centromere is a constriction region on the chromosome. In late pro phase, the chromosome appears to be solid and thicker and composed of a pair of chromatids. Each cremated is actually a package of DNA replication. In other words, paired chromatids are linked by a body of the centromere is a twin pack each copy (replica) DNA replication in the inter phase stage. The centromere is binding on both chromatids is considered as part of the DNA in the chromosomes that have not made the most recent replication and divide.

Meta phase. At the stage of metaphase chromosomes in pairs with each other. One pair of chromosomes consists of two chromosomes (2n). Each pair of chromatids of chromosomes made up of (2c) that put themselves on the field division. This field is a field placement division of chromosomes before dividing into polar the chromated cleavage. Thus, the chromosomes lie in the division with the goal of keeping the amount of DNA information to be given to the new daughter cells which really flat and the same amount.
Anaphase. At the stage of anaphase, chromatids begin to move towards the poles seem cleavage. Chromatid was unable to move itself, but must be withdrawn by the yarn from mikrotubul centrioles. Mikrotubul an interesting yarn called mikrotubul kinetochore chromosomes. Since the beginning of the core cleavage (early prophase), the yarn has been arranged in parallel mikrotubul linking centrioles to centrosome (the area near the nucleus of cells that normally contain centrioles) with the centromere through the kinetochore. Kinetochore is part of the chromosome (near the centromere) attachment for spindle threads. In animal cells, the field tends toward cleavage centrioles located at each pole of the cell. Each pole is the goal direction of movement of chromosomes (or chromatids, while it is in the attachment of the centromere). In plant cells there is no centrioles, but the division remains directed toward the pole of cleavage by a centrosome, but it does not contain threads sentriol. The way that mikrotubul chromosome kinetochore moves is by shortening mikrotubul. At the kinetochore, such mikrotubul dissociating (parsing) speed. Thus, the anaphase stage of producing a copy of the first but paired chromosomes (1c, 2n). Each copy of chromosome moves toward the pole division.

Telophase. In the early stages of telophase, the chromosomes (2n, and 1c) have been completed in polar division. Mikrotubul nonkinetokor (ie mikrotubul uninteresting chromosomes) extend the cell. Twin core has started core wrapped with envelope membranes. Chromatin threads started to loose. The final stage of telophase followed by cytokinesis.

Stage of cytokinesis. At the stage of cytokinesis occurs, followed by cytoplasmic division septum formation of new cells. Bulkhead separating the two nuclei into two daughter cells. In animal cells, cytokinesis begins during telophase stage ends. In late telophase occurred parsing spindle threads. Then immediately formed a narrow ring of microfilaments in the former region equatorial plane. This contraction in the direction in which cause deep cracks on the cell surface, followed by the contents of two cells permbagian separately. In plant cells have tough cell walls. Therefore, how cytokinesis of plant cells differ from animal cells. Plant cells that have been mengalam karokinesis bulkhead immediately formed around the former field of cell division. This bulkhead initially form from membrane vesicles derived from Golgi bodies. Vesicles are directed along mikrotubul in the equatorial plane. Vesicle-vesicle fusion was then experiencing the membrane form, and followed by the formation of new cell wall.


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