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12/9/14 Objective: What is the structure of a chromosome and what is its role in the cell cycle? Do Now: How many cells does mitosis produce?
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Cell Division: 1 cell divides into 2 identical DAUGHTER cells Getting from there to here…
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For reproduction –asexual reproduction one-celled organisms For growth –from fertilized egg to multi-celled organism For repair & renewal –replace cells that die from normal wear & tear or from injury Why do cells divide? amoeba
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Nucleus Cell Chromosomes Chromosomes are made of DNA!!
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Thread-like structures found in the nucleus of cells that contain DNA
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A combination of DNA and protein that make up a chromosome
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The Cell Cycle Interphase 90% of cell cycle cell doing its “everyday job” makes proteins, etc Prepares for duplication if triggered
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Interphase can be divided into subphases –G 1 phase –S phase –G 2 phase
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Interphase Divided into 3 phases: –G 1 = (Growth) cell grows –S = DNA Synthesis copies chromosomes –G 2 = (Growth) prepares for division cell grows (more) G0G0 signal to divide
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double- stranded mitotic human chromosomes
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Mitotic Phase - Stage where the cell is actually dividing
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Before you can share your notes, You have to make a copy
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-Chromatin condenses -Can see sister chromatids -Nuclear membrane breaks down -Spindle fibers form Prophase
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Protein fibers cross cell to form mitotic spindle –coordinates movement of chromosomes Microtubules: protein fibers that make up the spindle
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-Sister Chromatids: two identical joined chromosomes
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-Centromere: the region where the 2 chromatids are joined together
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Metaphase Chromosomes align along middle of cell –metaphase plate meta = middle plane –spindle fibers coordinate movement
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Anaphase Sister chromatids separate –move to opposite poles –pulled at centromeres
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Telophase Chromosomes arrive at opposite poles –Nuclear membrane reforms –Chromosomes disperse no longer visible under light microscope Spindle fibers disperse
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Cytokinesis Animals Splitting of cytoplasm cleavage furrow forms (shallow groove near old metaphase plate) splits cell in two
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Cytokinesis in Animals
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Mitosis in whitefish blastula
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Cytokinesis in Plants Plants –cell plate forms new cell wall
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The Cell Cycle Control System The sequential events of the cell cycle –Are directed by a distinct cell cycle control system, which is similar to a clock Control system G 2 checkpoint M checkpoint G 1 checkpoint G1G1 S G2G2 M
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The clock has specific checkpoints –Where the cell cycle stops until a go-ahead signal is received G 1 checkpoint G1G1 G1G1 G0G0 (a) If a cell receives a go-ahead signal at the G 1 checkpoint, the cell continues on in the cell cycle. (b) If a cell does not receive a go-ahead signal at the G 1 checkpoint, the cell exits the cell cycle and goes into G 0, a nondividing state. G0 phase: a non-dividing state
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Fig. 12-15 G1G1 G0G0 G 1 checkpoint (a)Cell receives a go-ahead signal G1G1 (b) Cell does not receive a go-ahead signal
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Cancer A disease caused by the disruption of the mechanism that normally controls the cell cycle Leads to uncontrolled cell divison
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Tumor A mass produced by out-of-control cell reproduction
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Types of Tumors Benign tumor: An abnormal mass of normal cells that can usually be removed by surgery Malignant tumor: masses of cells from the reproduction of cancer cells (can spread if not removed or killed)
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Metastasis The spread of cancer beyond their original site
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Prevention/Early Detection/Treatment
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Getting Started
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Interphase
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Prophase
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Metaphase
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Drawing Metaphase
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Anaphase
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Telophase
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Cytokinesis
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