Describe the process of mitosis that occurs during nuclear division.
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In mitotic division, the chromosome material in the nucleus is replicated. That is because the DNA which makes up the chromosomes can serve as a template to make more DNA. By making a second set of chromosomes during interphase, it will insure that at the end of mitotic division, each new daughter cell will have a full set of chromosomes. This will allow the two cells to carry out life activities and manufacture the proteins they need. After interphase, prophase occurs. The centrioles separate and a spindle begins to form.The nuclear membrane begins to disappear and the chromosomes are coiled and thickened. Next is metaphase. In this stage, the doubled chromosomes, called chromatids line up along in the equator of the cell. Their centromeres in the center attach to the spindle fibers that have formed. Next is anaphase. The doubled chromosomes separate and they move toward opposite poles. Next is telophase. The cell membrane pinches inward forming two separate cells. The nuclear membrane reforms in each new cell enclosing the chromosomes. If its an animal cell, cytokinesis occurs and the cell pinches in half. End result is two daughter cells, with the exact chromosome number as the parent cell. If it is a plant cell, a cell plate forms separating the two cells. And cytokinesis insures that half of the cytoplasm goes to each smaller but genetically identical cell.
Mitosis is defined as the type of cell division by which a single cell divides in such a way as to produce two genertically identical "daughter cells". This is the method by which the body produces new cells for both growth and repair of aging or damaged tissues throughout the body - as opposed to for sexual reproduction (when meiosis applies).
Mitosis is the simplest of the two ways (mitosis and meiosis) in which the nucleus of cells divide - as part of a process of cell division.
Mitosis (Nuclear Division):
Interphase:Interphase is not part of mitosis but is included here as a reminder that interphase preceeds mitosis.
Chromatin is a material located in the nucleus of a cells and resembling a thread-like mass. It exists in the form called "chromatin" when the cell is not dividing but forms chromosomes when the cell divides. Chromatin consists of DNA and protein. It can be stained with dyes in order to watch the process of mitosis using a light microscope.
Early in the prophase stage the chromatin fibres shorten into chromosomes that are visible under a light microscope. (Each prophase chromosome consists of a pair of identical double-stranded chromatids.)Later in prophase, the nucleolus disappears, the nuclear envelope breaks down, and the two centrosomes begin to form the miotic spindle (which is an assembly of microtubules).As the microtubules extend in length between the centrosomes, the centrosomes are pushed to opposite "poles" (extremes) of the cell.Eventually, the spindle extends between two opposite poles of the cell.
Metaphase is characterized by the "metaphase plate". This is a mid-point region within the cell that is formed/defined by the centromeres of the chromatid pairs aligning along the microtubules at the centre of the miotic spindle.
The centromeres split seperating the two members of each chromatid pair - which then move to the opposite poles of the cell: When they are seperated the chromatids are called chromosomes.As the chromosomes are pulled by the the microtubules during anaphase, they appear to be "V"-shaped because the centromeres lead the way, dragging the trailing arms of the chromosomes towards the pole/s.
Telophase begins after the chromosomal movement stops.The identical sets of chromosomes - which are by this stage at opposite poles of the cell, uncoil and revert to the long, thin, thread-like chromatin form.A new nuclear envelope forms around each chromatin mass.Nucleoli appear.Eventually the miotic spindle breaks-up.... then the cytoplasm begins to divide around the two new nuclei
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