Cell Reproduction Chromosomes Cell Division. Chromosomes ChromatinChromatin Structure...

Cell ReproductionCell Reproduction

ChromosomesChromosomes

Cell DivisionCell Division


• Chromatin StructureChromatin Structure

• Chromosome StructureChromosome Structure

• Chromosome CondensationChromosome Condensation

• Sister ChromatidsSister Chromatids

LearningLearningObjectivesObjectives

• TSW …TSW …1.1. Distinguish between chromatin & Distinguish between chromatin &

condensed chromosomescondensed chromosomes

2.2. Describe the location & structure Describe the location & structure of a chromosomeof a chromosome

3.3. Describe chromosome Describe chromosome condensationcondensation

4.4. Explain what sister chromatids areExplain what sister chromatids are


• Chromosome StructureChromosome Structure DNADNA – deoxyribonucleic acid – deoxyribonucleic acid ProteinsProteins

HistonesHistones• Serve as “spools” for long DNA moleculeServe as “spools” for long DNA molecule• Maintain chromosome shapeMaintain chromosome shape

Nonhistone proteinsNonhistone proteins• Control regional activity of DNAControl regional activity of DNA

• Chromosome FunctionChromosome Function Genetic CodeGenetic Code – hereditary material – hereditary material

When NOT involved in cell When NOT involved in cell division, chromosomes division, chromosomes exist as chromatin – a exist as chromatin – a mixture of DNA & proteins mixture of DNA & proteins w/in the nucleusw/in the nucleus

Chromosome Chromosome CondensationCondensation

coiling around histonescoiling around histones

coiling into supercoilscoiling into supercoils

further coiling into visible further coiling into visible structures (light microscope)structures (light microscope)

histoneshistones

Chromosome & Sister Chromosome & Sister ChromatidsChromatids

• Terminology:Terminology: centromerecentromere

constricted regionconstricted region of chromosome of chromosome

sister chromatids are sister chromatids are joinedjoined here here

kinetochorekinetochore – structure w/in centromere – structure w/in centromere where spindle microtubules attach to sister where spindle microtubules attach to sister chromatidschromatids

1 kinetochore for each chromatid1 kinetochore for each chromatid

Roles of Cell DivisionRoles of Cell Division

• Asexual ReproductionAsexual Reproduction prokaryotesprokaryotes protistansprotistans fungifungi

• Growth & DevelopmentGrowth & Development multicellular organismsmulticellular organisms

• Repair & RegenerationRepair & Regeneration multicellular organismsmulticellular organisms

plantsplants primitive animalsprimitive animals

Growth & DevelopmentGrowth & Development

Multicellular Multicellular OrganismsOrganisms

Fertilized eggFertilized egg

Ist divisionIst division

Early embryoEarly embryo

Late embryoLate embryo

FetusFetus

ToddlerToddler

Young childYoung child

Young adultYoung adult

Tissue RenewalTissue Renewal

Multicellular Multicellular OrganismsOrganismsbone marrow bone marrow

stem cellsstem cells

Tissue RepairTissue Repair

The Cell Cycle MovieThe Cell Cycle Movie

• To View Video:To View Video:– Move mouse cursor over slide title-linkMove mouse cursor over slide title-link– When hand appears, click onceWhen hand appears, click once

• MOV Video plays about 1 minMOV Video plays about 1 min

Cell DivisionCell Division

• The Cell CycleThe Cell Cycle InterphaseInterphase MitosisMitosis CytokinesisCytokinesis

LearningLearningObjectivesObjectives

• TSW …TSW …1.1. Describe each phase of the cell Describe each phase of the cell

cyclecycle

2.2. Summarize the phases of mitosisSummarize the phases of mitosis

3.3. Compare cytokinesis in plant & Compare cytokinesis in plant & animal cellsanimal cells

Cytoskeletal Elements of Cytoskeletal Elements of DivisionDivision

• Terminology:Terminology: centrosomecentrosome

microtubule organizing center (MTOC)microtubule organizing center (MTOC)

synthesizes synthesizes mitoticmitotic spindlespindle

centriolescentrioles

animal cells onlyanimal cells only

2/centrosome2/centrosome

9 sets of triplet microtubules arranged in 9 sets of triplet microtubules arranged in ringring

Mitotic Cell Cycle: Mitotic Cell Cycle: OverviewOverview

• Major StagesMajor Stages of Mitotic Cell of Mitotic Cell Division:Division: InterphaseInterphase

Divided into Divided into 3 phases3 phases

Mitosis (M phase)Mitosis (M phase)Divided into Divided into 4 main phases4 main phasesPhases Phases oftenoften subdivided subdivided

Cytokinesis (M phase)Cytokinesis (M phase)Animal cell processAnimal cell processPlant cell processPlant cell process

““mitotic phase” = mitotic phase” = division of the cell:division of the cell:

mitosismitosis

cytokinesiscytokinesis

InterphaseInterphase::Phases of InterphasePhases of Interphase

• Preparatory StagePreparatory Stage:: GG11 phase phase

cell growthcell growth; ; organelles duplicateorganelles duplicate; ; mitochondria & chloroplasts self-replicatemitochondria & chloroplasts self-replicate

S phaseS phaseDNA replicationDNA replication

GG22 phase phaseenzymes & other materialsenzymes & other materials necessary for necessary for

division division synthesizedsynthesized; cell growth ; cell growth continuescontinues

DNA ReplicationDNA Replication

InterphaseInterphase

InterphaseInterphase


• MOV Video plays about 25 secMOV Video plays about 25 sec

Phases of MitosisPhases of Mitosis

• PProphaserophase• PPrometaphaserometaphase• MMetaphaseetaphase• AAnaphasenaphase• TTelophaseelophase

PProud roud

PPittsburghittsburgh

MMadeade

AA

TTouchdownouchdown

A A

PneumonicPneumonic

Aide!Aide!

Mitosis: ProphaseMitosis: Prophase

• Division of the NucleusDivision of the Nucleus:: Early ProphaseEarly Prophase

chromosomes condensechromosomes condense as sister as sister chromatidschromatids

nucleoli dispersenucleoli dispersespindle apparatusspindle apparatus begins to form from begins to form from

centrosomes (centrosomes (MTOCMTOC))

Chromosome & Sister Chromosome & Sister ChromatidsChromatids

Mitosis:Mitosis:Early ProphaseEarly Prophase



Mitosis: Late ProphaseMitosis: Late Prophase

• Division of the NucleusDivision of the Nucleus:: Late ProphaseLate Prophase (Prometaphase) (Prometaphase)

nuclear envelope fragmentsnuclear envelope fragmentsmitotic spindle stretches across cellmitotic spindle stretches across cellspindle microtubulesspindle microtubules::

• Kinetochore tubulesKinetochore tubules – some – some attach to attach to chromosomeschromosomes at kinetochores at kinetochores

• Polar fibersPolar fibers – other microtubules stretch – other microtubules stretch toward poles toward poles

Mitosis:Mitosis:Late Prophase (Prometaphase)Late Prophase (Prometaphase)



Mitosis: MetaphaseMitosis: Metaphase

• Division of the NucleusDivision of the Nucleus: : (cont)(cont)

MetaphaseMetaphasespindlespindle across cell w/ centrosomes at across cell w/ centrosomes at

opposite polesopposite poleschromosomes line up acrosschromosomes line up across metaphasemetaphase

plateplate [ [cell equatorcell equator] ] with sister chromatids with sister chromatids on opposite sides of equatoron opposite sides of equator

• ““kinetochore tubules” attached to sister kinetochore tubules” attached to sister chromatidschromatids

• ““polar” microtubules span cell from equator to polar” microtubules span cell from equator to each poleeach pole

Spindle ApparatusSpindle Apparatus

CentrosomesCentrosomes

centrosomecentrosome

Kinetochore StructureKinetochore Structure

Mitosis:Mitosis:MetaphaseMetaphase



Mitosis: AnaphaseMitosis: Anaphase


AnaphaseAnaphasecentromeres separatecentromeres separatesister chromatids move to opposite cell sister chromatids move to opposite cell

polespoles as kinetochore tubules as kinetochore tubules shortenshortenPolar tubules Polar tubules lengthenlengthen to stretch cell to stretch cell

Kinetochore FunctionKinetochore Function

Mitosis:Mitosis:AnaphaseAnaphase



Mitosis: TelophaseMitosis: Telophase


(Early) Telophase(Early) Telophasepolar fibers polar fibers lengthenlengthen stretching cell stretching cellchromosomes (formerly sister chromosomes (formerly sister

chromatids) reach opposite poles of cellchromatids) reach opposite poles of cell

Mitosis: TelophaseMitosis: Telophase


(Late) Telophase(Late) Telophasedaughter nuclear envelopes reformdaughter nuclear envelopes reformdaughter nucleoli reformdaughter nucleoli reformchromosomeschromosomes decondensedecondense to to chromatinchromatin

Mitosis:Mitosis:TelophaseTelophase



CytokinesisCytokinesis

• Division of the CytoplasmDivision of the Cytoplasm:: Begins duringBegins during early telophaseearly telophase Finishes immediately Finishes immediately afterafter telophase telophase Daughter cells separated by different Daughter cells separated by different

mechanisms in plants & animalsmechanisms in plants & animals


• Cleavage furrowCleavage furrow formation: formation: animal cellsanimal cellsmicrofilaments attached to cell membrane microfilaments attached to cell membrane

shortenshortenCell isCell is pinched in twopinched in twoDaughter nuclei separatedDaughter nuclei separatedResults in 2 daughter cells with identical Results in 2 daughter cells with identical

genetic materialgenetic material

Mitotic Cell Division:Mitotic Cell Division:Time LapseTime Lapse


• ASF Video plays about 52 secASF Video plays about 52 sec

Review of Mitosis & Review of Mitosis & CytokinesisCytokinesis



Mitosis ReviewMitosis Review

Regulation of MitosisRegulation of Mitosis

CancerCancer

Cells & Human BiologyCells & Human Biology


• ASX Video plays about 16 minASX Video plays about 16 min

Compound Light Compound Light MicroscopeMicroscope Arm

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Cell Reproduction Chromosomes Cell Division. Chromosomes ChromatinChromatin Structure...

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