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transcript
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Reproduc)onattheCellularLevelBIOL160
Ch. 6
The Key Roles of Cell Division
• Celldivision
• Cellularreproduc)on
• Anabilityoforganismsthatbestdis)nguisheslivingthingsfrom
nonlivingmaAer
• Unicellularorganisms
• Cellulardivisionreproducestheen)reorganism
• Mul)cellularorganisms
• dependoncelldivisionfor:
• Developmentfromafer)lizedcell• Growth• Repair
• Cellcycle
• Lifeofacellfromforma)ontoitsowndivision
• Celldivisionisanintegralpart100 µm 200 µm 20 µm
(a) Reproduction (b) Growth and development
(c) Tissue renewal
Cell Division
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• Genome
• AlltheDNAinacell
• MaybeasingleDNAmolecule
• prokaryo)ccells
or…
• ManyDNAmolecules
• eukaryo)ccells
• Chromosomes
• PackagedDNAmoleculesinacell
• OnemoleculeofDNAequalsonechromosome
• Humanaverage51million-245millionbasepairsperchromosome
Cellular Organization of the Genetic Material
• Eacheukaryo)cspecies
• Hasacharacteris)cnumberofchromosomesineachcellnucleus
• Soma3ccells
• Non-reproduc)vecells
• havetwoofeachtypeofchromosome
• Diploid-46
• Germcells
• MakeGametes
• Reproduc)vecells:spermandeggs
• Onlyoneofeachchromosome
• Haploid-23
Cellular Organization of the Genetic Material
• Chroma3n
• ComplexofDNAandproteinthatcondensesduringcelldivision
• InEukaryo)cchromosomes
• TypicalDNAformwhennotac)velydividing
DNA Packaging
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• Prepara)onforcelldivision
• DNAisreplicatedandthe
chromosomescondense
• Sisterchroma3ds
• Duplicatedchromosome
• Twocopieswhichseparate
duringcelldivision
• Centromere
• Junc)onpointoftheduplicated
chromosome,wherethetwo
chroma)dsareaAached
Chromosome Distribution During Cell Division
Fig.12-4
0.5 µm Chromosomes
Chromosome duplication (including DNA synthesis)
Chromo- some arm
Centromere
Sister chromatids
DNA molecules
Separation of sister chromatids
Centromere
Sister chromatids
• Eukaryo)ccelldivisionconsistsof:
• Mitosis
• Divisionoftheduplicatedgenome
• Cytokinesis
• Divisionofthecytoplasmandsepara)onoforganelles
• Meiosis
• Avaria)onofcelldivisionformakinggametes
• Yieldsnoniden)caldaughtercells
• Onlyonesetofchromosomes,halfasmanyastheparentcell
• Haploid
Types of Eukaryotic Cell Division
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Phases of the Cell Cycle
• Thecellcycleconsistsof2phases
• Mito3c(M)phase
• mitosisandcytokinesis
• Interphase
• cellgrowth
• copyingofchromosomes
inprepara)onforcell
division
• Interphase
• about90%ofthecellcycle
• canbedividedinto
subphases:
• G1phase
• firstgap
• Sphase
• Synthesisof
duplicateDNA
• G2phase
• secondgap
Phases of the Cell Cycle - Interphase
S (DNA synthesis)
MITOTIC (M) PHASE
Mito
sis
Cytokinesis
G1
G2
• Mitosisisconven)onallydividedintofive
phases:
• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase
• Cytokinesisiswellunderwaybylate
telophase
Phases of the Cell Cycle - Mitotic Phase
PLAY
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Fig.12-6
G2 of Interphase
Centrosomes (with centriole pairs)
Chromatin (duplicated)
Nucleolus Nuclear envelope
Plasma membrane
Early mitotic spindle
Aster Centromere
Chromosome, consisting of two sister chromatids
Prophase Prometaphase
Fragments of nuclear envelope
Nonkinetochore microtubules
Kinetochore Kinetochore microtubule
Metaphase
Metaphase plate
Spindle Centrosome at one spindle pole
Anaphase
Daughter chromosomes
Telophase and Cytokinesis
Cleavage furrow
Nucleolus forming
Nuclear envelope forming
Phases of the Cell Cycle - Mitotic Phase
Prophase Prometaphase G2 of Interphase
Interphase
Prometaphase Prophase G2 of Interphase Nonkinetochore microtubules
Fragments of nuclear envelope
Aster Centromere Early mitotic spindle
Chromatin (duplicated)
Centrosomes (with centriole pairs)
Nucleolus Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Kinetochore Kinetochore microtubule
• Interphase(G2)
• Diffusechroma)n
• duplicatedstate
• Chromosomes
notvisibleunder
lightmicroscope
• Nucleoluss)ll
present
Prophase Prometaphase G2 of Interphase
Prometaphase Prophase G2 of Interphase
Nonkinetochore microtubules
Fragments of nuclear envelope
Aster Centromere Early mitotic spindle
Chromatin (duplicated)
Centrosomes (with centriole pairs)
Nucleolus Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Kinetochore Kinetochore microtubule
• Prophase
• Chroma)nbegins
tocondense
• Centrosomesbegin
tomigrate
• Spindlebeginsto
grow
Prophase
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Prophase Prometaphase G2 of Interphase
Prometaphase Prophase G2 of Interphase
Nonkinetochore microtubules
Fragments of nuclear envelope
Aster Centromere Early mitotic spindle
Chromatin (duplicated)
Centrosomes (with centriole pairs)
Nucleolus Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Kinetochore Kinetochore microtubule
• Prometaphase
• Chromsomesfullycondensed
• Nuclearmembranebrokendown
• Centrosomesestablishpoles
• SpindlefibersaAachtokinetochores
Prometaphase
Fig.12-6c
Metaphase Anaphase Telophase and Cytokinesis
Metaphase Anaphase Telophase and Cytokinesis
Cleavage furrow
Nucleolus forming
Metaphase plate
Centrosome at one spindle pole
Spindle Daughter chromosomes
Nuclear envelope forming
• Metaphase
• Chromosomesline
upatmetaphase
plate
• Singlefile
• Guidedby
spindlefibers
Metaphase
Fig.12-6c
Metaphase Anaphase Telophase and Cytokinesis
Metaphase Anaphase Telophase and Cytokinesis
Cleavage furrow
Nucleolus forming
Metaphase plate
Centrosome at one spindle pole
Spindle Daughter chromosomes
Nuclear envelope forming
• Anaphase
• Sisterchroma)ds
separate
• Now
daughter
chromosomes
• Migratetopoles
• Spindlefibers
shorten
Anaphase
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Fig.12-6c
Metaphase Anaphase Telophase and Cytokinesis
Metaphase Anaphase Telophase and Cytokinesis
Cleavage furrow
Nucleolus forming
Metaphase plate
Centrosome at one spindle pole
Spindle Daughter chromosomes
Nuclear envelope forming
• Telophase
• Daughter
chromosomes
reachpoles
• Beginto
decondense
• Nuclear
membranesform
• Cytokinesisbegins
• Cleavagefurrow
forms
Telophase
The Mitotic Spindle: A Closer Look • Mito3cspindle
• Apparatusofmicrotubulesthatcontrols
chromosomemovementduringmitosis
• Centrosome
• Microtubuleorganizingcenter
• Consistsoftwocentrioles
• Duringprophaseassemblesspindle
microtubules
• Thecentrosomereplicates
• formingtwocentrosomes
• migratetooppositeendsofthecell
• spindlemicrotubulesgrowoutfrom
them
Cytokinesis: A Closer Look
• Animalcells
• cytokinesisoccursbycleavage,formingacleavagefurrow
• Plantcells
• acellplateformsduringcytokinesis
Cleavage furrow 100 µm
Contractile ring of microfilaments
Daughter cells
(a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM)
Vesicles forming cell plate
Wall of parent cell
Cell plate
Daughter cells
New cell wall
1 µm
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Sea Urchin (Time Lapse)
Animal Mitosis
PLAY
PLAY
Mitosis and Cytokinesis
Binary Fission
• Prokaryotes(EubacteriaandArchaebacteria)
• Reproducebyatypeofcelldivisioncalledbinaryfission
• Singlechromosomereplicates(beginningattheoriginof
replica3on)
• twodaughterchromosomesac)velymoveapart
Fig.12-11-1
Origin of replication
Two copies of origin
E. coli cell Bacterial chromosome
Plasma membrane
Cell wall
Binary Fission
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Fig.12-11-2
Origin of replication
Two copies of origin
E. coli cell Bacterial chromosome
Plasma membrane
Cell wall
Origin Origin
Binary Fission
Fig.12-11-3
Origin of replication
Two copies of origin
E. coli cell Bacterial chromosome
Plasma membrane
Cell wall
Origin Origin
Binary Fission
Fig.12-11-4
Origin of replication
Two copies of origin
E. coli cell Bacterial chromosome
Plasma membrane
Cell wall
Origin Origin
Binary Fission
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Regulation of the Cell Cycle
• Thefrequencyofcelldivisionvarieswiththe
typeofcell
• Musclecells
• Neurons
• Hepatocytes
• Thesecellcycledifferencesresultfrom
regula)onatthemolecularlevel
• Signalingmolecules
The Cell Cycle Control System
S G1
M checkpoint
G2 M
Control system
G1 checkpoint
G2 checkpoint
• Cellcyclecontrolsystem
• Regulatedbybothinternalandexternalcontrols
• Hasspecificcheckpointswherethecellcyclestopsun)lago-ahead
signalisreceived
• G1checkpoint
• Appearsmostimportant
• cellreceivesago-aheadsignalattheG1checkpoint,itwillusuallycompletetheS,G2,andMphasesanddivide
• Nogo-aheadsignal
• Cellsexitscycle,switchingintoG0phase-anon-dividingstate
The Cell Cycle Control System
G1
G0
G1 checkpoint
(a) Cell receives a go-ahead signal
G1
(b) Cell does not receive a go-ahead signal
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Stop/Go Signs: Signals at the Checkpoints
• Internalsignal
• Mcheckpoint
• kinetochoresnotaAachedtospindlemicrotubules
• sendamolecularsignalthatdelaysanaphase
• Externalsignals
• Growthfactors
• proteinsreleasedbycertaincellsthats)mulateothercellstodivide
• platelet-derivedgrowthfactor(PDGF)s)mulatesthedivisionof
humanfibroblastcellsinculture
• Otherexternalsignals
• density-dependentinhibi3on
• crowdedcellsstopdividing
• anchoragedependence
• MostanimalcellsmustbeaAachedtoasubstratuminordertodivide
Stop/Go Signs: Signals at the Checkpoints
Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
(a) Normal mammalian cells (b) Cancer cells 25 µm 25 µm
Tumor
A tumor grows from a single cancer cell.
Glandular tissue
Lymph vessel
Blood vessel
Metastatic tumor
Cancer cell
Cancer cells invade neigh- boring tissue.
Cancer cells spread to other parts of the body.
Cancer cells may survive and establish a new tumor in another part of the body.
1 2 3 4
• Transforma3on• Anormalcellisconvertedtoacancerouscellwhichformstumors
• massesofabnormalcellswithinotherwisenormal)ssue• Benigntumor
• Abnormalcellsremainattheoriginalsite• Malignanttumors
• Invadesurrounding)ssues• Canmetastasizeexpor)ngcancercellstootherpartsofthebody,possiblyform
secondarytumors
Loss of Cell Cycle Controls in Cancer Cells
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You should now be able to: 1. Describethestructuralorganiza)onoftheprokaryo)cgenomeandtheeukaryo)c
genome
2. Listthephasesofthecellcycle;describethesequenceofeventsduringeachphase
3. Listthephasesofmitosisanddescribetheeventscharacteris)cofeachphase
4. Drawordescribethemito)cspindle,includingcentrosomes,kinetochore
microtubules,nonkinetochoremicrotubules,andasters
5. Comparecytokinesisinanimalsandplants
6. Describetheprocessofbinaryfissioninbacteriaandexplainhoweukaryo)cmitosis
mayhaveevolvedfrombinaryfission
7. Explainhowtheabnormalcelldivisionofcancerouscellsescapesnormalcellcycle
controls
8. Dis)nguishbetweenbenign,malignant,andmetasta)ctumors