cellular division: mitosis (text ch. 10, pp. 240-248)
TRANSCRIPT
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Cellular Division:Cellular Division:
MitosisMitosis
((Text Ch. 10, pp. 240-248Text Ch. 10, pp. 240-248))
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Reasons for Cell divisionReasons for Cell division
Basis of reproduction for all cellular organismsBasis of reproduction for all cellular organisms Enables multicellular organisms to growEnables multicellular organisms to grow Replaces worn-out or damaged cells and Replaces worn-out or damaged cells and
tissuetissue
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““Analysing Data”, p. 249Analysing Data”, p. 249
Life Span of Human CellsLife Span of Human Cells– 1. White blood cells: function vs lifespan1. White blood cells: function vs lifespan– 2. Consequences of injury to heart + spinal cord? Smooth 2. Consequences of injury to heart + spinal cord? Smooth
muscle?muscle?– 3. Hypothesis for data 3. Hypothesis for data – 4. Cancer: predict data table4. Cancer: predict data table
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Summary of Cell divisionSummary of Cell division
Prior to division, cell replicates all of Prior to division, cell replicates all of its DNAits DNA– One complete copy will go to each One complete copy will go to each
“daughter” cell“daughter” cell
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Recall:Recall:
genetic info for eukaryotic cells is genetic info for eukaryotic cells is contained in a contained in a membrane-bound membrane-bound nucleusnucleus
Before the cell can divide, the Before the cell can divide, the nucleus must also dividenucleus must also divide
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Recall:Recall:
Two types of cell division:Two types of cell division:– 1. Mitotic1. Mitotic
46 46 doubledouble 46 46 singlesingle chromosomes chromosomesAsexual, body cellsAsexual, body cells
– 2. 2. Meiotic Meiotic 46 double46 double 23 single23 single chromosomes chromosomesSexual cellsSexual cells
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Two Main Stages of Cell DivisionTwo Main Stages of Cell Division
1. Mitosis1. Mitosis::– division of the nucleus division of the nucleus – formsforms 2 daughter nuclei 2 daughter nuclei – each has aeach has a full, identical chromosome full, identical chromosome
set set 2. Cytokinesis2. Cytokinesis: :
– division of the cytoplasmdivision of the cytoplasm b/w 2 daughter b/w 2 daughter cellscells
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Cell CycleCell Cycle
Interphase ~ Interphase ~ 90% of time90% of time
Mitotic phase Mitotic phase ~10% of time~10% of time
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Nucleus contains DNA and proteinsNucleus contains DNA and proteins DNA packed tightly into DNA packed tightly into chromatinchromatin fibres fibres
Chromatin:Chromatin:– DNA coiled around DNA coiled around histone moleculeshistone molecules (protein) (protein)– Coils are then coiled into long fibres Coils are then coiled into long fibres
Fibres dispersed throughout nucleusFibres dispersed throughout nucleus
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Chromosome StructureChromosome Structure
Fig. 12-10, p. 297
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Chromosome Formation during Chromosome Formation during MitosisMitosis
Chromatin fibres gather + coilChromatin fibres gather + coil Bunched into compact Bunched into compact chromosomeschromosomes Set # of chromosomes per sp.Set # of chromosomes per sp.
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InterphaseInterphase Cell growth (G1)Cell growth (G1)
DNA synthesis (S)DNA synthesis (S)– Chromosomes Chromosomes
duplicate, still loosely duplicate, still loosely packedpacked
Produces proteins + Produces proteins + organelles for div. organelles for div. (G2)(G2)
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ProphaseProphase
Chromatin fibres Chromatin fibres condense into condense into chromosomeschromosomes– two “sister” two “sister”
chromatidschromatids– attached at a attached at a
narrow waist narrow waist ((centromerecentromere))
Spindles formSpindles form
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Prophase, cont’dProphase, cont’d
Centrioles at polesCentrioles at poles
Spindles grow, reach Spindles grow, reach chromosomeschromosomes
Nuclear envelope Nuclear envelope breaks down & breaks down & disappearsdisappears
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MetaphaseMetaphase
Chromosomes line Chromosomes line up along metaphase up along metaphase plate at centreplate at centre
Each Each chromatidchromatid connected at connected at centromere to a centromere to a spindle fibre from spindle fibre from each poleeach pole
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AnaphaseAnaphase
Centromeres split Centromeres split as spindle fibres as spindle fibres pull chromatids pull chromatids apartapart
Form group of Form group of single single chromosomes chromosomes at at each poleeach pole
Cell elongation Cell elongation beginsbegins
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TelophaseTelophase
Cells elongateCells elongate
Daughter nuclei Daughter nuclei appear at each pole appear at each pole as envelope re-formsas envelope re-forms
Chromatin fibres Chromatin fibres uncoiluncoil
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Telophase and CytokinesisTelophase and Cytokinesis
Cleavage furrow (animal)Cleavage furrow (animal)– Cell plate (plant)Cell plate (plant)
Cells contain ½ the cytoplasm, but same Cells contain ½ the cytoplasm, but same # chromosomes as parent cell# chromosomes as parent cell
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Mitosis in action:Mitosis in action:
http://www.teachersdomain.org/resohttp://www.teachersdomain.org/resource/tdc02.sci.life.stru.dnadivide/ urce/tdc02.sci.life.stru.dnadivide/
““Go Online” (p. 245 text)Go Online” (p. 245 text)
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Controls on Cell DivisionControls on Cell Division
Cell activity controlled by proteins Cell activity controlled by proteins (e.g. cyclins) and other regulators (e.g. cyclins) and other regulators – E.g. healing a cutE.g. healing a cut
What might happen without controls?What might happen without controls?– E.g. Cancer – how does it work?E.g. Cancer – how does it work?– http://http://www.youtube.com/watch?vwww.youtube.com/watch?v
=dK9UcjSPkLs&feature=related=dK9UcjSPkLs&feature=related