Lec Mitosis 2010

8/8/2019 Lec Mitosis 2010

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Cell Division andCell Division and

MitosisMitosis


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U nderstanding Cell DivisionU nderstanding Cell Division

What instructions are necessary forWhat instructions are necessary forinheritance?inheritance?

How are those instructions duplicated forHow are those instructions duplicated fordistribution into daughter cells?distribution into daughter cells?

By what mechanisms are instructionsBy what mechanisms are instructionsparceled out to daughter cells?parceled out to daughter cells?

What happens when things go wrong?What happens when things go wrong?


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R eproductionR eproduction

Parents produce a new generation of Parents produce a new generation of cells or multicelled individuals likecells or multicelled individuals like

themselvesthemselvesParents must provide daughter cellsParents must provide daughter cellswith hereditary instructions, encodedwith hereditary instructions, encoded

in DNA, and enough metabolicin DNA, and enough metabolicmachinery to start up their ownmachinery to start up their ownoperationoperation


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R oles of MitosisR oles of Mitosis

Multicelled organismsMulticelled organisms

GrowthGrowth Cell replacementCell replacement

Some protistans, fungi, plants,Some protistans, fungi, plants,

animalsanimals

Asexual reproductionAsexual reproduction


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ChromosomeChromosome

A DNA molecule & attached proteinsA DNA molecule & attached proteinsDuplicated in preparation for mitosisDuplicated in preparation for mitosis

one chromosome (unduplicated)

one chromosome (duplicated)


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Chromosome Number Chromosome Number

Sum total of chromosomes in a cellSum total of chromosomes in a cellSomatic cellsSomatic cells

Chromosome number is diploid (2Chromosome number is diploid (2 nn )) Two of each type of chromosomeTwo of each type of chromosome

GametesGametes Chromosome number is haploid (Chromosome number is haploid ( nn )) One of each chromosome typeOne of each chromosome type


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H uman Chromosome Number H uman Chromosome Number

Diploid chromosome number (2Diploid chromosome number (2 nn ) =) =4646

Two sets of 23 chromosomes eachTwo sets of 23 chromosomes each One set from fatherOne set from father One set from motherOne set from mother

Mitosis produces cells with 46Mitosis produces cells with 46chromosomeschromosomes-- --two of each typetwo of each type


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O rganization of ChromosomesO rganization of Chromosomes

DNA and proteins

arranged as cylindrical fiber

DNA

histone

one nucleosome

Figure 9.2Pa e 153


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Mitosis: Growth and DevelopmentMitosis: Growth and Development


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T he Development of a FrogT he Development of a Frog

VideoVideo

http://www.youtube.com/watch?v=dXpAbezdOho&feature=related


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InterphaseInterphase

Usually longest part of the cycleUsually longest part of the cycle

Cell increases in massCell increases in mass

Number of cytoplasmic componentsNumber of cytoplasmic components

doublesdoubles

DNA is duplicatedDNA is duplicated


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MitosisMitosis

Period of nuclear divisionPeriod of nuclear divisionUsually followed by cytoplasmic divisionUsually followed by cytoplasmic division

Four stages:Four stages:ProphaseProphase

MetaphaseMetaphaseAnaphaseAnaphase

TelophaseTelophase


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Control of the CycleControl of the Cycle

Once S begins, the cycleOnce S begins, the cycleautomatically runs through G2 andautomatically runs through G2 and

mitosismitosis

The cycle has a builtThe cycle has a built- -in molecularin molecular

brake in G1brake in G1Cancer involves a loss of control overCancer involves a loss of control overthe cycle, malfunction of thethe cycle, malfunction of the

brakes brakes


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topping the CycleStopping the Cycle

Some cells normally stop in interphaseSome cells normally stop in interphase

Neurons in human brainNeurons in human brain

Arrested cells do not divideArrested cells do not divide

Adverse conditions can stop cycleAdverse conditions can stop cycle

NutrientNutrient- -deprived amoebas get stuck indeprived amoebas get stuck in

interphaseinterphase


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T he Spindle ApparatusT he Spindle Apparatus

Consists of two distinct sets of Consists of two distinct sets of

microtubulesmicrotubules

Each set extends from one of the cellEach set extends from one of the cell

polespoles

Two sets overlap at spindle equatorTwo sets overlap at spindle equator

Moves chromosomes during mitosisMoves chromosomes during mitosis


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Spindle ApparatusSpindle Apparatus

one spindle pole

one of thecondensedchromosomes

spindle equator

microtubulesorganizedas a spindleapparatus

one spindle pole

Figure 9.5Pa e 155


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MaintainingMaintainingChromosomeChromosome

Number Number

mitosis, cytoplasmic divisionchromosome(unduplicated)in daughter cellat interphase

chromosome(unduplicated)in daughter cellat interphase

chromosome (unduplicated)in cell at interphase

same chromosome(duplicated) in interphaseprior to mitosis

Stepped Art

Figure 9.6Pa e 155


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Stages of MitosisStages of Mitosis

ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophase


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E arly ProphaseE arly Prophase - -

Mitosis BeginsMitosis BeginsDuplicated chromosomes begin toDuplicated chromosomes begin to

condensecondense

Figure 9.7Page 156


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Late ProphaseLate Prophase

New microtubules areNew microtubules areassembledassembledOne centriole pair isOne centriole pair ismoved towardmoved towardopposite pole of opposite pole of spindlespindle

Nuclear envelopeNuclear envelopestarts to break upstarts to break up

Figure 9.7Pa e 156


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T ransition to MetaphaseT ransition to Metaphase

Spindle formsSpindle forms

SpindleSpindlemicrotubulesmicrotubulesbecome attachedbecome attachedto the two sisterto the two sisterchromatids of chromatids of each chromosomeeach chromosome

Figure 9.7Page 156


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MetaphaseMetaphase

All chromosomesAll chromosomesare lined up atare lined up atthe spindlethe spindleequatorequatorChromosomesChromosomesare maximallyare maximallycondensedcondensed

Figure 9.7Page 156


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Anaphase Anaphase

Sister chromatidsSister chromatidsof eachof eachchromosome arechromosome arepulled apartpulled apartOnce separated,Once separated,each chromatideach chromatidis a chromosomeis a chromosome

Figure 9.7Page 156


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T elophaseT elophase

ChromosomesChromosomesdecondensedecondense

Two nuclearTwo nuclearmembranes form,membranes form,one around eachone around each

set of set of unduplicatedunduplicatedchromosomeschromosomes

Figure 9.7Page 156


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R esults of MitosisR esults of Mitosis

Two daughterTwo daughternucleinuclei

Each with sameEach with samechromosomechromosomenumber as parentnumber as parentcellcellChromosomes inChromosomes inunduplicated formunduplicated form

Figure 9.7Page 156


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O nion R oot T ip PreparationO nion R oot T ip Preparation

http://www.eastcentral.edu/acad/depts/BI/plant_mitosis_labels.html


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Mitosis VideoMitosis Video

http://www.youtube.com/watch?v=VlN7K1-9QB0


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Mitosis in the L illyMitosis in the L illy

http://faculty.pingry.org/thata/pingrhttp://faculty.pingry.org/thata/pingry_upload/movies/cellular_reproductiy_upload/movies/cellular_reproduction/plantcell_lily_mitosis.movon/plantcell_lily_mitosis.mov


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Cytoplasmic DivisionCytoplasmic Division

Usually occurs between lateUsually occurs between late

anaphase and end of telophaseanaphase and end of telophase

Two mechanismsTwo mechanisms

Cell plate formation (plants )Cell plate formation (plants )

Cleavage (animals )Cleavage (animals )


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Cell Plate FormationCell Plate Formation

Figure 9.8Page 158


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Animal Cell Division Animal Cell Division

Figure 9.9Pa e 159


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H e La CellsH e La Cells

Line of human cancer cells that canLine of human cancer cells that canbe grown in culturebe grown in culture

Descendents of tumor cells from aDescendents of tumor cells from awoman named Henrietta Lackswoman named Henrietta LacksLacks died at 31, but her cellsLacks died at 31, but her cellscontinue to live and divide in labscontinue to live and divide in labsaround the worldaround the world


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Immortal Cell L ineImmortal Cell L ine

He LaHe La cells divide very rapidly evencells divide very rapidly evencompared to other cancer cellscompared to other cancer cells

HelaHela cells have a the ability tocells have a the ability toprotect the chromosomes telomeresprotect the chromosomes telomeres the result is thatthe result is that He LaHe La cells dontcells dontageageHe LaHe La cells have an unusual numbercells have an unusual numberof chromosomesof chromosomes 8484-- and containand containthe genome of the Humanthe genome of the Human PapillomaPapilloma

Virus (H PV)Virus (H PV)

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Lec Mitosis 2010