How Body Cells Reproduce The Cell Cycle Mitosis

This is a continuous cycle of growth and division. 2 Phases: -Growth (Interphase) -Division (Mitosis)

Interphase (Growth)  This is the growth phase in which cells make new molecules to increase its volume and mass.  The cell is constantly synthesizing RNA and producing protein.  This lasts anywhere from hours.  Further divided into G1, S and G2 phase.

Phases of Interphase G1: Gap 1, period of rapid growth and metabolic activity. S : Synthesis phase, DNA synthesis and Replication G2: Gap 2, centrioles replicate and cell prepares for cell division. Go: There are times when a cell will leave the cycle and quit dividing. This may be a temporary resting period or more permanent.

Mitosis (Division)  Shortest part of the cell cycle.  Occurs in all somatic (body) cells.  What is the Purpose? - Growth - Repair damaged tissues - Replace old or damaged cells

Mitosis  One cell divides to produce 2 identical daughter cells with the exact same number of chromosomes as the parent cell.  There are four phases: - Prophase - Metaphase - Anaphase - Telophase

Prophase  Chromatin (DNA and Protein) condenses and thickens to form visible chromosomes.  Each X shaped chromosome contains 2 copies of the original chromosome.  Each copy is called a chromatid.  While they are attached, they are considered to be ONE chromosome.

Prophase  Nuclear membrane and nucleolus disappear.  Centrioles migrate to opposite poles.  Spindle fibres form between the two centrioles.

Metaphase  Spindle fibers attached to centromere (where the two chromatids are attached) of replicated chromosomes.  Chromosomes line up in the middle of cell also known as the equator.

Anaphase  Centromere splits  Chromatids are pulled to opposite poles of the cell.

Telophase  The chromatids have now reached the opposite poles of the cell.  Each chromotid is now called a chromosome.  Chromosomes unwind and become less visible.

Cytokinesis (Actual cell division)  Cytoplasm separates and a new cell membrane or cell wall is formed to create two new daughter cells.  Nucleolus and nuclear membrane reappear.

Questions  Do all cells go through the cell cycle at the same rate?  What would happen if the chromosomes did not duplicate during interphase?  Do sex cells go through mitosis?

Error in Mitosis (Mutations)  Mutagens such as toxic compounds, radiation or viruses can cause mutations.  Mutations cause a permanent error or change in the normal DNA molecule that can be passed on to daughter cells during anaphase.  Usually found in a localized group of cells.

Examples  If the FHIT gene which is located on chromosome #3 is mutated, it causes lung cells to undergo mitosis more frequently and results in a tumour.  Oncogenes are genes that can be activated by a mutation and effect the cells rate of mitosis.  If cells divide uncontrollably and rapidly, tumours can develop and these tumours may become cancerous.

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