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The Cell The Cell CycleCycle

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Cell DivisionCell Division

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

• New cells are produced for New cells are produced for growthgrowth and to replace and to replace damaged or old cellsdamaged or old cells

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

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Eukaryotic Eukaryotic ChromosomesChromosomes• Human body cellsHuman body cells have have 4646

chromosomes or 23 identical pairschromosomes or 23 identical pairs• Each chromosome is composed of a Each chromosome is composed of a

single,single, tightly coiled DNAtightly coiled DNA molecule molecule

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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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KaryotypeKaryotype• A 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 called autosomesautosomes

• Last pair are the Last pair are the sex chromosomessex chromosomes

• XXXX female or female or XYXY malemale

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Cell Cell ReproductionReproduction

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Types of Cell Types of Cell ReproductionReproduction

• Asexual reproductionAsexual reproduction involves a involves a single cellsingle cell dividing to make dividing to make 2 2 new, identical daughter new, identical daughter cellscells

• Examples: Mitosis & Examples: Mitosis & binary fissionbinary fission

• Sexual reproductionSexual reproduction involves involves making two cells (egg & making two cells (egg & sperm).sperm).

• Example: Meiosis Example: Meiosis • FertilizationFertilization involves joining involves joining

of egg & sperm to make a of egg & sperm to make a new cell (zygote)new cell (zygote)

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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

Parent Parent cellcell

2 identical daughter 2 identical daughter cellscells

ChromosoChromosome me

replicatesreplicates

Cell Cell splitssplits

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The Cell The Cell CycleCycle

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Five Phases of the Cell Five Phases of the Cell CycleCycle

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

InterphaseInterphase

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Interphase - GInterphase - G11 Stage Stage

• 11stst growth stage growth stage after cell after cell divisiondivision

• Cells Cells maturemature by making by making more cytoplasm & more cytoplasm & organellesorganelles

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Interphase – S StageInterphase – S Stage• SynthesisSynthesis stage stage• DNADNA is copied or is copied or replicatedreplicated

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 Stage• Occurs Occurs after DNA has been after DNA has been

copiedcopied• All cell All cell structures needed structures needed

for divisionfor division are made (e.g. are made (e.g. centrioles)centrioles)

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The Cell CycleThe Cell Cycle

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

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MitosisMitosis• Division of the Division of the

nucleusnucleus• Only occurs in Only occurs in

eukaryoteseukaryotes• Has Has fourfour

stagesstages• Doesn’t occur Doesn’t occur

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

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Four Mitotic StagesFour Mitotic Stages

1.1. ProProphasephase

2.2. MetaMetaphasphasee

3.3. AnaAnaphasephase

4.4. TeloTelophasephase

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ProphaseProphase• ChromatinChromatin in nucleus condenses in nucleus condenses

to form to form visible chromosomesvisible chromosomes• Nuclear membrane & nucleolusNuclear membrane & nucleolus

are broken downare broken down

ChromosomesChromosomes

NucleolusNucleolus CytoplasmCytoplasm

Nuclear MembraneNuclear Membrane

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MetaphaseMetaphase• Chromosomes move to the center Chromosomes move to the center

of the cellof 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

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AnaphaseAnaphase• Occurs Occurs

rapidlyrapidly• Sister Sister

chromatidschromatids are pulled are pulled apart to apart to opposite opposite polespoles

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AnaphaseAnaphase

Sister Sister ChromatidChromatid

s being s being separatedseparated

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TelophaseTelophase• Sister chromatids at Sister chromatids at opposite opposite polespoles• Nuclear envelopeNuclear envelope forms forms around each set of sister around each set of sister chromatidschromatids• NucleolusNucleolus reappears reappears• CYTOKINESISCYTOKINESIS occurs occurs• Chromosomes reappear as Chromosomes reappear as chromatinchromatin

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CytokinesisCytokinesis•Means division of the Means division of the

cytoplasmcytoplasm•DivisionDivision 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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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

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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 cells Produce two new cells identical to the original identical to the original cellcell

• Cells are Cells are diploid (2n)diploid (2n)Chromosomes Chromosomes

during Metaphase during Metaphase of mitosisof mitosis

ProphaProphasese

MetaphaseMetaphase AnaphaseAnaphaseTelophaseTelophaseCytokinesisCytokinesis

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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 cell unlimited cell division occurs division occurs causing cancerous causing cancerous tumorstumors

• OncogenesOncogenes are are special proteins special proteins that increase the chance increase the chance that a normal cell that a normal cell develops into adevelops into a tumor cell tumor cell

Cancer Cancer cellscells