( GENETICS ) Cell Cycle & Cell Division

8/7/2019 ( GENETICS ) Cell Cycle & Cell Division

1/66

1

CellularCellular

DivisionDivision


2/66

2

Cell DivisionCell Division

All cells are derived fromAll cells are derived from prepre--existingexisting cellscellsNew cells are produced forNew cells are produced forgrowthgrowth and to replaceand to replace damaged ordamaged orold cellsold cellsDiffers inDiffers in prokaryotesprokaryotes (bacteria)(bacteria)andand eukaryoteseukaryotes (protists, fungi,(protists, fungi,plants, & animals)plants, & animals)


3/66


4/66

4

Identical Daughter CellsIdentical Daughter Cells

Parent CellParent Cell

TwoTwo

identicalidentical

daughterdaughter

cellscells


5/66

5

Cell ReproductionCell Reproduction


6/66

6

Types of Cell ReproductionTypes of Cell ReproductionAsexual reproductionAsexual reproduction involves ainvolves asingle cellsingle cell dividing to makedividing to make 2 new,2 new,identical daughter cellsidentical daughter cellsMitosis & binary fissionMitosis & binary fission areareexamples of asexual reproductionexamples of asexual reproductionSexual reproductionSexual reproduction involves twoinvolves twocells (egg & sperm) joining to make acells (egg & sperm) joining to make a

new cell (zygote)new cell (zygote) that isthat is NOTNOTidentical to the original cellsidentical to the original cellsMeiosisMeiosis is an exampleis an example


7/66

7

The CellThe Cell

CycleCycle


8/66

8

Five Phases of the Cell CycleFive Phases of the Cell Cycle

GG11 -- primary growth phaseprimary growth phaseSS synthesis; DNA replicatedsynthesis; DNA replicatedGG

22 -- secondary growth phasesecondary growth phasecollectively thesecollectively these 33 stages arestages arecalled interphasecalled interphase

MM -- mitosismitosisCC -- cytokinesiscytokinesis


9/66

9

Cell CycleCell Cycle


10/66

10

InterphaseInterphase -- GG11 StageStage

11stst growth stagegrowth stage after cellafter celldivisiondivision

CellsCells maturemature by making moreby making morecytoplasm & organellescytoplasm & organelles

Cell carries on itsCell carries on its normalnormal

metabolic activitiesmetabolic activities


11/66

11

InterphaseInterphase S StageS Stage

SynthesisSynthesis stagestageDNADNA is copied oris copied or replicatedreplicated

TwoTwoidenticalidenticalcopiescopiesof DNAof DNA

OriginalOriginal

DNA

DNA


12/66

12

InterphaseInterphase GG22 StageStage

22ndnd GrowthGrowth StageStageOccursOccurs after DNA has been copiedafter DNA has been copied

All cell

All cell structures needed forstructures needed fordivisiondivision are made (e.g. centrioles)are made (e.g. centrioles)

BothBoth organelles & proteinsorganelles & proteins areare

synthesizedsynthesized


13/66

13

Whats Happening in Interphase?Whats Happening in Interphase?

What the cell looks likeWhat the cell looks like

Animal Cell

Whats occurring


14/66

14

Sketch the Cell CycleSketch the Cell Cycle

DaughterDaughterCellsCells

DNA CopiedDNA Copied

CellsCells

MatureMature

Cells prepare forCells prepare forDivisionDivision

Cell Divides intoCell Divides intoIdentical cellsIdentical cells


15/66

15

MitosisMitosis


16/66

16

MitosisMitosisDivision of theDivision of thenucleusnucleusAlso calledAlso calledkaryokinesiskaryokinesisOnly occurs inOnly occurs ineukaryoteseukaryotesHasHas fourfour stagesstagesDoesnt occur inDoesnt occur insome cells suchsome cells suchasas brain cellsbrain cells


17/66

17

Four Mitotic StagesFour Mitotic Stages

ProProphasephase

MetaMetaphasephaseAnaAnaphasephase

TeloTelophasephase


18/66

18

Early ProphaseEarly ProphaseChromatinChromatin in nucleus condenses toin nucleus condenses toformform visible chromosomesvisible chromosomesMitotic spindleMitotic spindle forms from fibers informs from fibers incytoskeleton orcytoskeleton or centrioles (animal)centrioles (animal)

ChromosomesChromosomes

NucleolusNucleolus CytoplasmCytoplasm

Nuclear MembraneNuclear Membrane


19/66

19

Late ProphaseLate Prophase

Nuclear membrane & nucleolusNuclear membrane & nucleolus arearebroken downbroken down

ChromosomesChromosomes continue condensing &continue condensing &

areare clearly visibleclearly visibleSpindle fibers calledSpindle fibers called kinetochoreskinetochoresattach to the centromereattach to the centromere of eachof each

chromosomechromosomeSpindleSpindle finishes forming between thefinishes forming between thepoles of the cellpoles of the cell


20/66

20

Late ProphaseLate Prophase

Nucleus & Nucleolus have disintegratedNucleus & Nucleolus have disintegrated

ChromosomesChromosomes


21/66

21

Review of ProphaseReview of Prophase

What the cellWhat the celllooks likelooks like

Whats happeningWhats happening


22/66

22

MetaphaseMetaphaseChromosomes, attached to theChromosomes, attached to thekinetochore fiberskinetochore fibers, move to the center, move to the centerof the cellof the cell

Chromosomes are now lined up at theChromosomes are now lined up at the

equatorequator

Pole ofPole ofthe Cellthe Cell

Equator of CellEquator of Cell


23/66

23

MetaphaseMetaphase

ChromosomesChromosomeslined at thelined at theEquatorEquator

SpindleSpindleFibersFibers


24/66

24

MetaphaseMetaphase

Chromosomes at EquatorChromosomes at Equator


25/66

25

Review of MetaphaseReview of Metaphase

What the cell looksWhat the cell lookslikelike

WhatsWhatsoccurringoccurring


26/66


27/66

27

AnaphaseAnaphase

SisterSister

ChromatidsChromatidsbeingbeing

separatedseparated


28/66

28

Anaphase ReviewAnaphase Review

What theWhat thecell lookscell looks

likelike

WhatsWhatsoccurringoccurring


29/66

29

TelophaseTelophaseSister chromatids atSister chromatids at oppositeoppositepolespolesSpindleSpindle disassemblesdisassemblesNuclear envelopeNuclear envelope forms aroundforms aroundeach set of sister chromatidseach set of sister chromatidsNucleolusNucleolus reappearsreappearsCYTOKINESISCYTOKINESIS occursoccursChromosomes reappear asChromosomes reappear aschromatinchromatin


30/66

30

Comparison of Anaphase & TelophaseComparison of Anaphase & Telophase


31/66

31

CytokinesisCytokinesisMeans division of the cytoplasmMeans division of the cytoplasmDivisionDivision of cell into two,of cell into two,identical halves calledidentical halves called daughterdaughter

cellscellsIn plant cells, cell plateIn plant cells, cell plate formsformsat the equator to divide cellat the equator to divide cell

In animal cells,In animal cells, cleavage furrowcleavage furrowforms to split cellforms to split cell


32/66

32

CytokinesisCytokinesis

Cleavage furrowCleavage furrowin animal cellin animal cell

Cell plate inCell plate inplant cellplant cell


33/66

33

Mitotic StagesMitotic Stages


34/66

34

Daughter Cells of MitosisDaughter Cells of MitosisHave theHave the same number ofsame number ofchromosomes as each otherchromosomes as each other and asand asthe parent cellthe parent cell from which theyfrom which theywere formedwere formed

IdenticalIdentical to each other, butto each other, but smallersmallerthan parent cellthan parent cell

MustMust grow in sizegrow in size to become matureto become maturecellscells (G(G11 of Interphase)of Interphase)


35/66

35

Eukaryotic Cell DivisionEukaryotic Cell Division

Used forUsed for growth andgrowth andrepairrepair

Produce two new cellsProduce two new cellsidentical to the originalidentical to the originalcellcell

Cells areCells are diploid (2n)diploid (2n)

Chromosomes duringChromosomes duringMetaphase of mitosisMetaphase of mitosis

ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophaseCytokinesisCytokinesis


36/66

36

Mitosis AnimationMitosis AnimationName each stage as you see it occur?Name each stage as you see it occur?


37/66

37

Name the Stages of Mitosis:Name the Stages of Mitosis:

Interphase

Early prophase

Mid-ProphaseLateProphase

Metaphase

LateAnaphase

Early Anaphase

Early

Telophase,Begin

cytokinesis

Late telophase,Advancedcytokinesis


38/66

38

Identify the StagesIdentify the Stages

Early, Middle, & Late ProphaseEarly, Middle, & Late Prophase

Late ProphaseLate Prophase MetaphaseMetaphase AnaphaseAnaphase

Late

Anaphase

Late

Anaphase

Telophase

Telophase

Telophase &Telophase &CytokinesisCytokinesis

??

?? ?? ??

?? ?? ??


39/66

39

MeiosisMeiosis

Formation of GametesFormation of Gametes(Eggs & Sperm)(Eggs & Sperm)


40/66

40

Facts About MeiosisFacts About Meiosis

Preceded byPreceded by interphaseinterphase whichwhichincludesincludes chromosome replicationchromosome replication

TwoTwo meiotic divisionsmeiotic divisions ------ MeiosisMeiosis

I and Meiosis III and Meiosis IICalled ReductionCalled Reduction-- divisiondivision

Original cell is diploid (Original cell is diploid (22n)n)

Four daughter cellsFour daughter cells produced thatproduced thatareare haploid (haploid (monoploidmonoploid) () (11n)n)


41/66

41

Facts About MeiosisFacts About MeiosisDaughter cellsDaughter cells contain half thecontain half thenumber of chromosomesnumber of chromosomes as theas theoriginal celloriginal cell

ProducesProduces gametesgametes ((eggs & spermeggs & sperm))Occurs in theOccurs in the testestestes in malesin males((SpermatogenesisSpermatogenesis))

Occurs in theOccurs in the ovariesovaries in femalesin females((OogenesisOogenesis))

Reduce the amount of geneticReduce the amount of genetic

material by one halfmaterial by one half


42/66

42

Start withStart with 4646 double strandeddouble strandedchromosomes (chromosomes (22n)n)AfterAfter 11 divisiondivision -- 2323 doubledouble

stranded chromosomes (n)stranded chromosomes (n)AfterAfter 22nd divisionnd division -- 2323 singlesinglestranded chromosomes (n)stranded chromosomes (n) Occurs in ourOccurs in our germ cellsgerm cells thatthatproduce gametesproduce gametes

More Meiosis FactsMore Meiosis Facts


43/66

43

Why Do we Need Meiosis?Why Do we Need Meiosis?

It is the fundamental basis ofIt is the fundamental basis ofsexual reproductionsexual reproductionTwo haploid (1n) gametes areTwo haploid (1n) gametes are

brought together throughbrought together throughfertilizationfertilization to form a diploidto form a diploid(2n) zygote(2n) zygote

F tili tiF tili ti P tti itP tti it


44/66

44

FertilizationFertilization Putting itPutting itall togetherall together

1n =31n =3

22n =n = 66


45/66

45

Replication of ChromosomesReplication of ChromosomesReplicationReplication is theis theprocess ofprocess ofduplicating aduplicating achromosomechromosome

OccursOccurs prior toprior todivisiondivision

Replicated copiesReplicated copiesare calledare called sistersisterchromatidschromatids

Held together atHeld together atcentromerecentromere

Occurs inOccurs inInterphaseInterphase


46/66

46

A Replicated ChromosomeA Replicated Chromosome

HomologsHomologs((same genes,same genes,

different alleles)different alleles)

SisterSister

ChromatidsChromatids((same genes,same genes,same alleles)same alleles)

Gene XGene X

Homologs separate in meiosis I andHomologs separate in meiosis I andtherefore different alleles separate.therefore different alleles separate.


47/66

47

Meiosis Forms Haploid GametesMeiosis Forms Haploid Gametes

Meiosis mustMeiosis must reduce the chromosome numberreduce the chromosome numberby halfby halfFertilization then restoresFertilization then restores thethe 22n numbern number

from mom from dad child

meiosis reducesgenetic content

too

much!

The right

number!


48/66

48

Meiosis: Two Part CellMeiosis: Two Part Cell

DivisionDivisionHomologsHomologsseparateseparate

SisterSisterchromatidschromatidsseparateseparate

DiploidDiploid

MeiosisMeiosisII

MeiosisMeiosisIIII

DiploidDiploid

HaploidHaploid


49/66

49

Meiosis I: Reduction DivisionMeiosis I: Reduction Division

NucleusNucleus SpindleSpindlefibersfibers NuclearNuclear

envelopeenvelopeEarlyEarly

Prophase IProphase I((ChromosomeChromosome

numbernumberdoubleddoubled))

LateLateProphaseProphase

II

MetaphaseMetaphaseII AnaphaseAnaphase

IITelophase ITelophase I((haploid)haploid)

Pr ph s IPr ph s I


50/66

50

Prophase IProphase I

Early prophaseEarly prophaseHomologs pair.Homologs pair.Crossing overCrossing overoccursoccurs.

Late prophaseLate prophase

Chromosomes condense.Chromosomes condense.Spindle forms.Spindle forms.Nuclear envelopeNuclear envelopefragments.fragments.


51/66

C iC i OO


52/66

52

CrossingCrossing--OverOverHomologousHomologous

chromosomeschromosomes inina tetrada tetrad crosscrossover each otherover each other

Pieces ofPieces ofchromosomes orchromosomes orgenes aregenes areexchangedexchanged

ProducesProducesGeneticGeneticrecombinationrecombination ininthe offspringthe offspring

H l ChH l Ch


53/66

53

Homologous ChromosomesHomologous Chromosomes

During CrossingDuring Crossing--OverOver

C iC i OO


54/66

54

CrossingCrossing--over multiplies the already hugeover multiplies the already hugenumber of different gamete typesnumber of different gamete types

produced by independent assortmentproduced by independent assortment

CrossingCrossing--OverOver

Metaphase IMetaphase I


55/66

55

Metaphase IMetaphase I

Homologous pairsHomologous pairs

of chromosomesof chromosomesalign along thealign along theequatorequator of theof the

cellcell

Anaphase IAnaphase I


56/66

56

Anaphase IAnaphase I

Homologs separateHomologs separate andandmove to opposite poles.move to opposite poles.

Sister chromatidsSister chromatids remainremain

attachedattached at theirat theircentromerescentromeres.

Telophase ITelophase I


57/66

57

Telophase ITelophase I

Nuclear envelopesNuclear envelopesreassemble.reassemble.

Spindle disappears.Spindle disappears.

CytokinesisCytokinesis divides celldivides cellinto two.into two.

M i i IIM i i II


58/66

58

Meiosis IIMeiosis II

Only one homolog of eachOnly one homolog of eachchromosome is present inchromosome is present inthe cellthe cell.

Meiosis II produces gametes withMeiosis II produces gametes withone copy of each chromosome andone copy of each chromosome andthus one copy of each gene.thus one copy of each gene.

Sister chromatids carrySister chromatids carry

identical geneticidentical geneticinformationinformation..

Gene XGene X

M i i II R d iM i i II R d i


59/66

59

Meiosis II: ReducingMeiosis II: Reducing

Chromosome NumberChromosome Number

ProphaseProphaseIIII

MetaphaseMetaphaseIIII

AnaphaseAnaphaseIIII

TelophaseTelophaseIIII 44 IdenticalIdentical

haploid cellshaploid cells

P h IIP h II


60/66

60

Prophase IIProphase II

Nuclear envelopeNuclear envelope

fragments.fragments.Spindle forms.Spindle forms.

M t h IIM t h II


61/66

61

Metaphase IIMetaphase II

Chromosomes alignChromosomes alignalongalong equatorequator of cellof cell..

A h IIA h II


62/66

62

Anaphase IIAnaphase II

Sister chromatidsSister chromatidsseparate andseparate andmove tomove to oppositeopposite

polespoles.

EquatorEquator

PolePole

T l h IIT l h II


63/66

63

Telophase IITelophase II

Nuclear envelopeNuclear envelopeassembles.assembles.

ChromosomesChromosomesdecondense.decondense.

Spindle disappears.Spindle disappears.

Cytokinesis dividesCytokinesis dividescell into two.cell into two.

R lt f M i iR lt f M i i


64/66

64

Results of MeiosisResults of MeiosisGametes (egg & sperm)Gametes (egg & sperm)

formform

Four haploid cells withFour haploid cells withone copy of eachone copy of each

chromosomechromosome

One allele of each geneOne allele of each gene

Different combinationsDifferent combinationsof alleles for differentof alleles for differentgenes along thegenes along thechromosomechromosome


65/66

65

ComparingComparing

Mitosis andMitosis andMeiosisMeiosis

C mp ris n f Divisi nsC mp ris n f Divisi ns


66/66

MitosisMitosis MeiosisMeiosis

Number ofNumber ofdivisionsdivisions

1122

Number ofNumber of

daughter cellsdaughter cells

22 44

GeneticallyGeneticallyidentical?identical?

YesYes NoNo

Chromosome #Chromosome # Same as parentSame as parent Half of parentHalf of parent

WhereWhere Somatic cellsSomatic cells Germ cellsGerm cells

WhenWhen Throughout lifeThroughout life At sexual maturityAt sexual maturity

RoleRoleGrowth andGrowth and

Sexual reproductionSexual reproduction

Comparison of DivisionsComparison of Divisions

Documents

( GENETICS ) Cell Cycle & Cell Division