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Published byLesley Wright Modified over 9 years ago
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Bell Ringer 1.Why do cells need to divide in multicellular organisms? 2.What is the difference between prokaryotes and eukaryotes with regard to chromosomes? 3.What does a human chromosome consist of? Draw one! Label. 4.Describe a role of chromatin in chromosome in your own words.
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DNA and Chromosomes Chromatin Histones DN A The function of chromatin is to efficiently package DNA
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Cell Cycle Cell Cycle is a sequence of events through which a cell progresses during its lifetime
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Cell can be either in dividing (Mitotic Phase) or non-dividing state (Interphase)
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Interphase about 90% of the cell cycle
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G1 Phase (Gap 1): Cell Growth Protein Synthesis Cell Metabolism Preparation for S Phase
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S Phase (synthesis): – DNA is replicated
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G2 Phase (Gap 2): Further Cell Growth Protein Synthesis Specialized proteins needed for Cell Division
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The cell grows during all three phases, but chromosomes are duplicated only during the S phase
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Mitotic Phase
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Mitosis: Prophase Metaphase Anaphase Telophase
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Cytokinesis is division of cytoplasm/cell: – cleavage furrow forms in animal cells – cell plate (cell wall) forms in plant cells – daughter cells are identical
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Figure 12.10a (a) Cleavage of an animal cell (SEM) Cleavage furrow Contractile ring of microfilaments Daughter cells 100 m
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Figure 12.10b (b) Cell plate formation in a plant cell (TEM) Vesicles forming cell plate Wall of parent cell Cell plate New cell wall Daughter cells 1 m
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Cell Cycle Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis
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Interphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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Prophase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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Prophase The cell prepares for nuclear division Animal and Plant Cell – Packages DNA into chromosomes – nuclear envelope breaks down – Centrosomes move apart and forms spindle which guides chr. separation
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Metaphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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Metaphase The cell prepares chromosomes for division Animal and Plant Cell – Chromosomes line up at the center of the cell – Spindle fibers attach from daughter cells to chromosomes at the centromere
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Anaphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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Anaphase The chromosomes divide Animal and Animal Cell – Spindle fibers pull chromosomes apart – ½ of each chromosome (called chromotid) moves to each daughter cell
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Telophase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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Telophase The cytoplasm divides Animal Cell – chromosomes uncoil – 2 nuclei form – spindle breaks down – nuclear envelope and – nucleoli reappear
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