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CellularCellular
DivisionDivision
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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)
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Identical Daughter CellsIdentical Daughter Cells
Parent CellParent Cell
TwoTwo
identicalidentical
daughterdaughter
cellscells
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Cell ReproductionCell Reproduction
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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
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The CellThe Cell
CycleCycle
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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
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Cell CycleCell Cycle
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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
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InterphaseInterphase S StageS Stage
SynthesisSynthesis stagestageDNADNA is copied oris copied or replicatedreplicated
TwoTwoidenticalidenticalcopiescopiesof DNAof DNA
OriginalOriginal
DNA
DNA
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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
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Whats Happening in Interphase?Whats Happening in Interphase?
What the cell looks likeWhat the cell looks like
Animal Cell
Whats occurring
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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
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MitosisMitosis
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MitosisMitosisDivision of theDivision of thenucleusnucleusAlso calledAlso calledkaryokinesiskaryokinesisOnly occurs inOnly occurs ineukaryoteseukaryotesHasHas fourfour stagesstagesDoesnt occur inDoesnt occur insome cells suchsome cells suchasas brain cellsbrain cells
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Four Mitotic StagesFour Mitotic Stages
ProProphasephase
MetaMetaphasephaseAnaAnaphasephase
TeloTelophasephase
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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
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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
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Late ProphaseLate Prophase
Nucleus & Nucleolus have disintegratedNucleus & Nucleolus have disintegrated
ChromosomesChromosomes
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Review of ProphaseReview of Prophase
What the cellWhat the celllooks likelooks like
Whats happeningWhats happening
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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
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MetaphaseMetaphase
ChromosomesChromosomeslined at thelined at theEquatorEquator
SpindleSpindleFibersFibers
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MetaphaseMetaphase
Chromosomes at EquatorChromosomes at Equator
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Review of MetaphaseReview of Metaphase
What the cell looksWhat the cell lookslikelike
WhatsWhatsoccurringoccurring
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AnaphaseAnaphase
SisterSister
ChromatidsChromatidsbeingbeing
separatedseparated
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Anaphase ReviewAnaphase Review
What theWhat thecell lookscell looks
likelike
WhatsWhatsoccurringoccurring
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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
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Comparison of Anaphase & TelophaseComparison of Anaphase & Telophase
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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
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CytokinesisCytokinesis
Cleavage furrowCleavage furrowin animal cellin animal cell
Cell plate inCell plate inplant cellplant cell
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Mitotic StagesMitotic Stages
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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)
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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
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Mitosis AnimationMitosis AnimationName each stage as you see it occur?Name each stage as you see it occur?
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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
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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
??
?? ?? ??
?? ?? ??
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MeiosisMeiosis
Formation of GametesFormation of Gametes(Eggs & Sperm)(Eggs & Sperm)
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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)
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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
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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
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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
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FertilizationFertilization Putting itPutting itall togetherall together
1n =31n =3
22n =n = 66
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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
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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.
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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!
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Meiosis: Two Part CellMeiosis: Two Part Cell
DivisionDivisionHomologsHomologsseparateseparate
SisterSisterchromatidschromatidsseparateseparate
DiploidDiploid
MeiosisMeiosisII
MeiosisMeiosisIIII
DiploidDiploid
HaploidHaploid
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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
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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.
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C iC i OO
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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
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Homologous ChromosomesHomologous Chromosomes
During CrossingDuring Crossing--OverOver
C iC i OO
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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
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Metaphase IMetaphase I
Homologous pairsHomologous pairs
of chromosomesof chromosomesalign along thealign along theequatorequator of theof the
cellcell
Anaphase IAnaphase I
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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
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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
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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
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Meiosis II: ReducingMeiosis II: Reducing
Chromosome NumberChromosome Number
ProphaseProphaseIIII
MetaphaseMetaphaseIIII
AnaphaseAnaphaseIIII
TelophaseTelophaseIIII 44 IdenticalIdentical
haploid cellshaploid cells
P h IIP h II
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Prophase IIProphase II
Nuclear envelopeNuclear envelope
fragments.fragments.Spindle forms.Spindle forms.
M t h IIM t h II
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Metaphase IIMetaphase II
Chromosomes alignChromosomes alignalongalong equatorequator of cellof cell..
A h IIA h II
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Anaphase IIAnaphase II
Sister chromatidsSister chromatidsseparate andseparate andmove tomove to oppositeopposite
polespoles.
EquatorEquator
PolePole
T l h IIT l h II
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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
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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
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ComparingComparing
Mitosis andMitosis andMeiosisMeiosis
C mp ris n f Divisi nsC mp ris n f Divisi ns
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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