Mitosis and Cell Cycle

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Mitosis and Cell Cycle
1 Daughter Cells
1.1 Produces 2 daughter nuclei that have the same number of chromosomes as the parent cell and each other.
1.2 There are different number of chromosomes in Mitosis and Meiosis. Meiosis conatins four daughter nuclei, each with half the number of chromosomes.
1.3 Its different because Mitosis replicates the cell whereas Meiosis divides.
2 Stages of Mitosis
2.1 1. Prophase; in which the chromosomes become visible and nuclear envelope disappears.
2.2 2. Metaphase; the chromosomes arrange themselves at the centre of the cell. (Spindle)
2.3 3. Anaphase; each of the two threads of a chromosome (chromatid) migrates to an opposite pole.
2.4 4. Telophase; In which the nuclear envelope reforms
2.5 Interphase: Mitosis is always preceded by a period during which the cell is not dividing. It is a period of considerable cellular activity that includes the replication of DNA.
3 Uses of Mitosis
3.1 Growth; When two haploid cells fuse together to form a diploid cell (contains all the information needed to form a new organism). If the new organism is to resemble its parents all the cells that grow from the original must possess the same set of genetic information.
3.2 Differentiation; These cells change to give groups of specialised cells e.g epithelium in animals or xylem in plants. These different cell types each divide by mitosis to give tissues made up to identical cells which perform a paticular function. This is essential as the tissue can only function efficiently if all its cells have the same structure and perform the same function
3.3 Repair; If cells die or are damaged it is important that the new cells have identical stucture and function. If they are not exact copies the tissue would not function effectively as before. Therefore Mitosis helps replace damaged or dead cells.
4 Cell Cycle
4.1 1. Interphase; which occupies most of the cell cycle and is sometimes known as the resting phase because no division takes place;
4.1.1 a. First Growth (G1) when the proteins from which cell organelles are synthesised are produced
4.1.2 b. Synthesis (S) when DNA is replicated
4.1.3 c. Second Growth (G2) When organelles grow and divide and energy stores are increased
4.2 2. Nuclear division when the nucleus divides either into 2 (mitosis) or four (meiosis)
4.3 The length of 1 cell cycle depends on the cell. Typically a mammlian cell takes about 24 hours to complete of which 90% is interphase.
4.4 Cancer; caused by a growth disorder of cells. It is a result of damage to the genes that regulate mitosis and the cell cycle.This leads to uncontrolled growth of cells. As a result a tumour develops and constantly expands in size.

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