Wednesday, January 12, 2011

Mitosis! :)

In the Mitosis process, there are six stages starting with interphase.  Interphase is where the chromatin is undifferentiated in the heavily-stained nucleus.  Before a cell begins mitosis, it has to undergo a synthesis phase where every chromosome is duplicated and is made up of two sister chromatids joined by a specific DNA sequence known as a centromere.
The first initial phase of mitosis is called prophase.  The nuclear chromatin starts to be organized and forms into thick strands that eventually become chromosomes.  During this stage, the cytoskeleton begins to break down and the main piece of the mitotic apparatus, the mitotic spindle begins to shape outside the nucleus at opposite ends of the cell.  
early prophase
The next phase is metaphase, or the middle of all the stages.  Metaphase is when the chromosomes, attached to the "kinetochore microtubules," begin to align in one plane halfway between the spindle poles.  The microtubules apply a pull on the chromosomes and the entire spindle-chromosome complex is ready for the next phase.  In metaphase, the kinetochore and polar microtubules are clearly seen and radiate out the ends of the cell which leave the chromosomes in the middle of the complex.
metaphase
After metaphase, the cell begins anaphase.  After the metaphase chromosomes are aligned at the metaphase plate, the two halves of chromosomes are pulled apart by the spindle apparatus and move to the opposite spindle poles.  As the chromosomes are pulled toward the poles the kinetochore microtubules shrink, while the polar microtubules lengthen to assist in seperating.  Anaphase is the fastest stage in mitosis.  
Anaphase
The last stage of Mitosis is called Telophase.  In this stage, the daughter chromosomes arrive at the spindle poles and are finally redistributed into chromatin.  Cytokinesis also continues through telophase.  After the chromosomes are completely separated and their extrusion to the spindle poles, the nuclear membrane begins to reform around each group of chromosomes at the opposite ends of the cell.
Telophase
Overall Mitosis is a fairly long process and at the end it results into two daughter cells.  The process then starts all over again.
http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html



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