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Cellular Cellular DivisionDivision

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Cell DivisionCell Division

All cells are derived fromAll cells are derived from pre-existingpre-existing cellscells

Two new daughter cells are Two new daughter cells are produced for produced for growthgrowth and to and to replace damaged or old cellsreplace damaged or old cells

Differs inDiffers in prokaryotesprokaryotes (bacteria) and(bacteria) and eukaryoteseukaryotes (protists, fungi, plants, & (protists, fungi, plants, & animals)animals)

Why do cells divide?

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• Average Human Adult: ~75 trillion cells• Average Human Infant: ~4.3 trillion

cells

*YOUR CELLS ARE THE SAME SIZE… YOU JUST HAVE MORE FO THEM THANKS TO MITOSIS!

***Surface Area-to-Volume Ratio• Volume increases faster than surface

area• Puts strain on metabolic functions• Nutrients and waste are not transported

efficiently• Larger organisms do not necessarily

have bigger cells… just more of them

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Keeping Cells IdenticalKeeping Cells Identical

TheThe instructions instructions for making cell for making cell partsparts are encoded are encoded in the in the DNADNA, so , so each new cell each new cell must get amust get a complete set of complete set of the DNA the DNA moleculesmolecules

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DNA ReplicationDNA ReplicationDNA must be DNA must be

copied orcopied or replicated replicated before cell before cell divisiondivision

Each new cell Each new cell will then have will then have anan identical identical copycopy of the of the DNADNA

Original DNA Original DNA strandstrand

Two new, Two new, identical DNA identical DNA

strandsstrands

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Identical Daughter Identical Daughter CellsCells

Parent CellParent Cell

Two Two identical identical daughter daughter

cellscells

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Prokaryotic ChromosomeProkaryotic Chromosome

The DNA of The DNA of prokaryotes prokaryotes (bacteria) is (bacteria) is one, circular one, circular chromosome chromosome attached to attached to the inside of the inside of the cell the cell membranemembrane

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Eukaryotic Eukaryotic ChromosomesChromosomesAll All eukaryoticeukaryotic cells store cells store

genetic information in genetic information in chromosomeschromosomes

Most eukaryotes have between Most eukaryotes have between 10 10 and 50 chromosomesand 50 chromosomes in their body in their body cellscells

Human body cells have 46 Human body cells have 46 chromosomeschromosomes or 23 identical pairs or 23 identical pairs

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Chromosomes in Dividing Chromosomes in Dividing CellsCells

Duplicated chromosomes are called chromatids & are held together by the centromere

Called Sister Called Sister ChromatidsChromatids

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KaryotypeKaryotypeA A picturepicture of the of the

chromosomes chromosomes from a human cell from a human cell arranged in pairs arranged in pairs by sizeby size

First 22 pairs are First 22 pairs are called autosomescalled autosomes

Last pair are the Last pair are the sex chromosomessex chromosomes

XXXX female or female or XYXY malemale

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Boy or Girl?Boy or Girl?

Y - Y - ChromosomeChromosome

X - X - ChromosomeChromosome

TheThe Y Chromosome Y Chromosome DecidesDecides

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Cell Cell ReproductionReproduction

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Types of Cell Types of Cell ReproductionReproductionAsexual reproductionAsexual reproduction involves a involves a

single cellsingle cell dividing to make dividing to make 2 2 new, identical daughter cellsnew, identical daughter cellsMitosis & binary fission are examples of Mitosis & binary fission are examples of

asexual reproductionasexual reproduction

Sexual reproductionSexual reproduction involves involves two cells (egg & sperm) joining two cells (egg & sperm) joining to make a to make a new cell (zygote)new cell (zygote) that that is is NOT identical to the original NOT identical to the original cellscellsMeiosis is a type of sexual reproductionMeiosis is a type of sexual reproduction

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Cell Division in Cell Division in ProkaryotesProkaryotes

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Cell Division in Cell Division in ProkaryotesProkaryotes Prokaryotes such Prokaryotes such

as as bacteriabacteria divide divide into 2 identical into 2 identical cells by the cells by the process of process of binary binary fissionfission

Single chromosome Single chromosome makes a copy of makes a copy of itselfitself

Cell wall forms Cell wall forms between the between the chromosomes chromosomes dividing the celldividing the cell

Parent Parent cellcell

2 identical daughter 2 identical daughter cellscells

ChromosoChromosome me

relicatesrelicates

Cell Cell splitssplits

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Animation of Binary Animation of Binary FissionFission

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Prokaryotic Cell Prokaryotic Cell Undergoing Binary Undergoing Binary

FissionFission

Mitochondria and chloroplasts reproduce similarly

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The Cell The Cell CycleCycle

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Five Phases of the Cell CycleFive Phases of the Cell Cycle

1.1. GG11 - primary growth phase - primary growth phase2.2. S – synthesis; DNA replicatedS – synthesis; DNA replicated

3.3. GG22 - secondary growth phase - secondary growth phasecollectively these 3 stages are collectively these 3 stages are called interphasecalled interphase

4.4. M - mitosisM - mitosis5.5. C - cytokinesisC - cytokinesis

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Cell CycleCell Cycle

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Interphase - GInterphase - G11 Stage Stage11stst growth stage growth stage after cell after cell

divisiondivisionCells spend the majority of Cells spend the majority of

time in this phasetime in this phaseCells Cells maturemature by making more by making more

cytoplasm & organellescytoplasm & organellesCell carries on its Cell carries on its normal normal

metabolic activitiesmetabolic activities

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InterphaseInterphase – S Stage – S StageSynthesisSynthesis stage stageDNA is copied or replicatedDNA is copied or replicated

Two Two identicidentic

al al copies copies of DNAof DNA

Original Original DNADNA

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Interphase – GInterphase – G22 Stage Stage

22ndnd Growth Growth Stage StageOccurs Occurs after DNA has been after DNA has been

copiedcopiedAll cell All cell structures needed for structures needed for

division (M)division (M) are made (e.g. are made (e.g. centrioles)centrioles)

Both Both organelles & proteinsorganelles & proteins are are synthesizedsynthesized

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What’s Happening in What’s Happening in Interphase?Interphase?

What the cell looks likeWhat the cell looks like

Animal Cell

What’s occurring

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Draw and Label the Cell Draw and Label the Cell CycleCycle

DaughteDaughter Cellsr Cells

DNA DNA CopiedCopied

Cells Cells MaturMatur

ee

Cells prepare Cells prepare for Divisionfor Division

Cell Divides into Cell Divides into Identical cellsIdentical cells

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MitosisMitosis

MICROTUBULESDIPLOID

Sister Chromatids separateDIPLOID

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MitosisMitosisDivision of the Division of the

nucleusnucleusAlso called Also called

karyokinesiskaryokinesisOnly occurs in Only occurs in

eukaryoteseukaryotesHas Has fourfour phases phasesDoesn’t occur Doesn’t occur

in some cells in some cells such as such as brain brain cellscells

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Four Mitotic Phases: PMATFour Mitotic Phases: PMAT

ProProphasephaseMetaMetaphasephaseAnaAnaphasephaseTeloTelophasephase

THEN:THEN:

CytokinesisCytokinesis

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Four Mitotic Phases: PMATFour Mitotic Phases: PMAT

ProProphase: phase: Pro = first/ Pro = first/ beforebefore

MetaMetaphase: phase: Meta - middleMeta - middle

AnaAnaphase: phase: Ana = back; awayAna = back; away

TeloTelophase: phase: Telo Telo = = distantdistant

Cytokinesis = Cytokinesis = cyto = cell; kine cyto = cell; kine = cut= cut

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Early ProphaseEarly ProphaseChromatinChromatin in nucleus condenses to in nucleus condenses to

form form visible chromosomesvisible chromosomesMitotic spindle Mitotic spindle forms from fibers in forms from fibers in

cytoskeleton or cytoskeleton or centrioles (animal)centrioles (animal)

ChromosomesChromosomes

NucleolusNucleolus CytoplasmCytoplasm

Nuclear MembraneNuclear Membrane

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Late ProphaseLate ProphaseNuclear membrane & nucleolusNuclear membrane & nucleolus

are broken downare broken downChromosomesChromosomes continue continue

condensing & are condensing & are clearly visibleclearly visibleSpindle fibers called Spindle fibers called

kinetochoreskinetochores attach to the attach to the centromerecentromere of each chromosome of each chromosome

SpindleSpindle finishes forming finishes forming between the between the poles of the cellpoles of the cell

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Late ProphaseLate Prophase

Nucleus & Nucleolus have disintegratedNucleus & Nucleolus have disintegrated

ChromosomeChromosomes s

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MetaphaseMetaphaseChromosomes, attached to the Chromosomes, attached to the

kinetochore fiberskinetochore fibers, move to the , move to the center of the cellcenter of the cell

Chromosomes are now lined up at Chromosomes are now lined up at the equatorthe equator

Pole of Pole of the Cellthe Cell

Equator of CellEquator of Cell

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MetaphaseMetaphase

ChromosoChromosomes lined mes lined at the at the EquatorEquator

Asters at Asters at the polesthe poles

Spindle Spindle FibersFibers

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MetaphaseMetaphase

AsterAster

Chromosomes at EquatorChromosomes at Equator

Mitotic Spindle =

centrioles + spindle fibers

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AnaphaseAnaphaseOccurs Occurs rapidlyrapidlySister Sister

chromatidschromatids are pulled are pulled apart to apart to opposite polesopposite poles of the cell by of the cell by kinetochore kinetochore fibersfibers

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AnaphaseAnaphase

Sister Sister ChromatidChromatid

s being s being separatedseparated

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TelophaseTelophaseSister chromatids at Sister chromatids at opposite opposite polespoles

Spindle Spindle disassemblesdisassemblesNuclear envelopeNuclear envelope forms forms around each set of sister around each set of sister chromatidschromatids

NucleolusNucleolus reappears reappearsCYTOKINESISCYTOKINESIS occurs occursChromosomes reappear as Chromosomes reappear as chromatinchromatin

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Comparison of Anaphase & Comparison of Anaphase & TelophaseTelophase

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CytokinesisCytokinesisCytokinesis means Cytokinesis means division of division of

the cytoplasmthe cytoplasmDivisionDivision of cell into two, of cell into two,

identical halves called identical halves called daughter cellsdaughter cells

In plant cells, cell plate In plant cells, cell plate forms forms at the equator to divide cellat the equator to divide cell

In animal cells, In animal cells, cleavage cleavage furrow forms to split cellfurrow forms to split cell

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CytokinesisCytokinesis

Cleavage Cleavage furrow in furrow in

animal cellanimal cell

Cell plate in Cell plate in plant cellplant cell

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Mitotic StagesMitotic Stages

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Daughter Cells of MitosisDaughter Cells of MitosisHave the Have the same number of same number of

chromosomes as each otherchromosomes as each other and as the parent celland as the parent cell from from which they were formedwhich they were formed

IdenticalIdentical to each other, but to each other, but smaller than parent cellsmaller than parent cell

Must grow in size Must grow in size to become to become mature cells mature cells (G(G11 of Interphase) of Interphase)

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Identical Daughter CellsIdentical Daughter Cells

Chromosome number the Chromosome number the samesame, but , but cells cells smallersmaller than parent cell than parent cell

What What is the is the 2n or 2n or

diploid diploid numbenumbe

r?r?22

Cell Cycle - review• Interphase

– G1:– S:– G2:

• Mitosis– P:– M:– A:– T:

• Cytokinesis

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RevieReview of w of

MitosiMitosiss

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Eukaryotic Cell DivisionEukaryotic Cell Division

Used for Used for growth and growth and repairrepair

Produce two new Produce two new cells cells identical to the identical to the original celloriginal cell

Cells are Cells are diploiddiploid (2n) (2n)

Chromosomes Chromosomes during Metaphase during Metaphase

of mitosisof mitosis

ProphaProphasese

MetaphaseMetaphase AnaphaseAnaphaseTelophaseTelophaseCytokinesisCytokinesis

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

occur?occur?

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Mitosis in Onion Root Mitosis in Onion Root TipsTips

Do you see any stages of mitosis?Do you see any stages of mitosis?

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Identify the StagesIdentify the Stages

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

Late Late ProphaseProphase

MetaphaseMetaphase AnaphaseAnaphase

Late Late AnaphaseAnaphase

TelophaseTelophase Telophase & Telophase & CytokinesisCytokinesis

??

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Locate the Four Mitotic Locate the Four Mitotic Stages in PlantsStages in Plants

MetaphasMetaphasee

ProphaseProphase

AnaphaAnaphasese

TelophaseTelophase

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Uncontrolled Mitosis If mitosis is not If mitosis is not

controlledcontrolled, unlimited , unlimited cell division occurs cell division occurs causing causing cancerous cancerous tumorstumors

OncogenesOncogenes code for code for special proteins special proteins that increase the chance increase the chance that a normal cell that a normal cell develops into a develops into a tumor cell… tumor cell… genes genes that regulate cell that regulate cell divisiondivision

Cancer Cancer cellscells

CANCER = MITOSIS GONE AWRY

Cancer Animations

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Mitosis Yarn Lab• MAX 2 people per laminated sheet• You will only use cells A, B, and C for

today• See me if you need more yarn

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