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Cell Cycle Cell Cycle – Overview A.  Interphase: first, and longest stage of the cell cycle, during which the cell grows, replicates its DNA, and prepares to divide. The phases of interphase are shown below. Cell Cycle – Overview 1.  G0 Phase 2.  G1 Phase 3.  S Phase 4.  G2 Phase Cell Cycle – Overview B.  MitoJc Phase: second stage of the cell cycle, during which the nucleus is divided. The phases of mitosis are shown below. Cell Cycle – Overview 1.  Prophase 2.  Metaphase 3.  Anaphase 4.  Telophase Cell Cycle – Overview C.  Cytokinesis: the final stage of the cell cycle, during which the cytoplasm divides to form two idenJcal daughter cells. Cell Cycle – Specifics A.  Interphase 1.  G0 Phase: temporary resJng period or permanent phase of a cell when the cell stops dividing. Not all cells do this. Cell Cycle – Specifics 2.  G1 Phase: the cell grows in size, produces RNA, and synthesizes proteins. 3.  S Phase: DNA synthesis occurs. 4.  G2 Phase: the cell grows in size, produces RNA, and synthesizes proteins. **Organelles and molecules required for cell division are produced. Cell Cycle – Specifics B.  MitoJc Phase 1.  Prophase: nuclear envelope breaks down and DNA condenses into chromosome form. Tiny structures called centrioles begin to move toward the poles of the cell. Cell Cycle – Specifics 2.  Metaphase: chromosomes line up in the middle of the cell. The centrioles produce spindle fibers, which aRach to the chromosomes’ centromere. Cell Cycle – Specifics 3.  Anaphase: chromosomes are pulled apart as the spindle fibers shorten. The sister chromaJds are separated as they move towards opposite poles of the cell. Cell Cycle – Specifics 4.  Telophase: sister chromaJds arrive at the poles of the cell. The spindle fibers begin to disappear and the nuclear envelope reforms.. Cell Cycle – Specifics •  Cytokinesis: cytoplasm is divided and two new, idenJcal daughter cells are formed. The chromosomes return to the chromaJn state. Extra Information •  Remember – mitosis is an example of asexual reproducJon as it creates exact copies from one parent cell. •  Cells have a sweet spot/perfect size. When a cell becomes too large, it will divide or enter G0 and stop growing. •  Chromosomes make is possible to separate DNA precisely during cell division. Extra Information –  Purpose of mitosis is to replace worn-­‐out cells, enable mulJcellular organisms to grow, keep total cell number of a mature organism relaJvely constant. –  Enzymes begin and drive the cell cycle. –  Cells that lose control (uncontrolled dividing of cells) leads to cancer. –  If a cell realizes it has been made incorrectly, it will self destrucJon itself to avoid further harm to the organism. Back to Notes •  Complete the Cell Cycle IllustraJon page of your notes by using the textbook. •  Complete the Cell Cycle QuesJon page of your notes using your understanding of the cell cycle.