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Cell ReproductionCell Reproduction
ChromosomesChromosomes
Cell DivisionCell Division
Meiotic Cell CycleMeiotic Cell Cycle
Mitosis Introduction
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• ASX Video plays about 14-1/4 minASX Video plays about 14-1/4 min• A Video Quiz is included in the A Video Quiz is included in the
presentationpresentation
ChromosomesChromosomes
• Chromosome StructureChromosome Structure
• Chromosome NumbersChromosome Numbers Sex Chromosomes & AutosomesSex Chromosomes & Autosomes Diploid & Haploid CellsDiploid & Haploid Cells KaryotypingKaryotyping
LearningLearningObjectivesObjectives
• TSW …TSW …1.1. Describe the structure of a Describe the structure of a
chromosomechromosome2.2. Compare prokaryotic Compare prokaryotic
chromosomes w/ eukaryotic chromosomes w/ eukaryotic chromosomeschromosomes
3.3. Explain the difference btw/ sex Explain the difference btw/ sex chromosomes & autosomeschromosomes & autosomes
4.4. Give examples of haploid & diploid Give examples of haploid & diploid cellscells
ChromosomesChromosomes
• Chromosome StructureChromosome Structure DNADNA – deoxyribonucleic acid – deoxyribonucleic acid ProteinsProteins
HistonesHistones• Serve as “spools” for long DNA moleculeServe as “spools” for long DNA molecule• Maintain chromosome shapeMaintain chromosome shape
Nonhistone proteinsNonhistone proteins• Control regional activity of DNAControl regional activity of DNA
• Chromosome FunctionChromosome Function Genetic CodeGenetic Code – hereditary material – hereditary material
When NOT involved in cell When NOT involved in cell division, chromosomes division, chromosomes exist as chromatin – a exist as chromatin – a mixture of DNA & proteins mixture of DNA & proteins w/in the nucleusw/in the nucleus
Chromosome Chromosome CondensationCondensation
coiling around histonescoiling around histones
coiling into supercoilscoiling into supercoils
further coiling into visible further coiling into visible structures (light microscope)structures (light microscope)
histoneshistones
Chromosome & Sister Chromosome & Sister ChromatidsChromatids
• Terminology:Terminology: centromerecentromere
constricted regionconstricted region of chromosome of chromosome
sister chromatids are sister chromatids are joinedjoined here here
kinetochorekinetochore – structure w/in centromere – structure w/in centromere where spindle microtubules attach to sister where spindle microtubules attach to sister chromatidschromatids
1 kinetochore for each chromatid1 kinetochore for each chromatid
ChromosomeChromosomeNumbersNumbers
• Chromosome NumberChromosome Number Characteristic for each speciesCharacteristic for each species
2 different species may have the same 2 different species may have the same chromosome numberchromosome number• Chimpanzees & gorillas w/Chimpanzees & gorillas w/ 4848 – both – both
apes; closely relatedapes; closely related• Potatoes & gorillas w/ Potatoes & gorillas w/ 4848 – not closely – not closely
relatedrelated
Types of AnimalTypes of AnimalChromosomesChromosomes
• Sex ChromosomesSex Chromosomes (1 pair = 2 in humans)(1 pair = 2 in humans) Chromosomes that carry genes for sexual Chromosomes that carry genes for sexual
expressionexpressionDetermine the sex of an organismDetermine the sex of an organism
May carry genes for other charactersMay carry genes for other characters Human Sex Chromosomes Human Sex Chromosomes – “X” & “Y”– “X” & “Y”
XXXX = female= femaleXYXY = male= male
• AutosomesAutosomes (22 pairs = 44 in humans)(22 pairs = 44 in humans) Carry genes for Carry genes for mostmost characters characters
HomologousHomologousChromosomesChromosomes
• Karyotype Karyotype – displays homologues– displays homologues• Homologous ChromosomesHomologous Chromosomes
chromosome pairs of the chromosome pairs of the same lengthsame length, , centromere positioncentromere position, and , and staining staining patternpattern that posses that posses genes for the genes for the same characterssame charactersone homologue is inherited from the one homologue is inherited from the
organism’s organism’s fatherfatherone homologue is inherited from the one homologue is inherited from the
organism’s organism’s mothermother
Homologous Homologous ChromosomesChromosomes
ChromosomeChromosomeSetsSets
• Haploid CellsHaploid Cells 1 set1 set of chromosomesof chromosomes Symbol = Symbol = nn
In humansIn humans, n = , n = 2323In fruit fly, n = 4In fruit fly, n = 4
• Diploid CellsDiploid Cells 2 sets2 sets of chromosomesof chromosomes Symbol = Symbol = 2n2n
In humansIn humans, 2n = , 2n = 4646In fruit fly, 2n = 8In fruit fly, 2n = 8
KaryotypeKaryotype
• Homologous Chromosomes Homologous Chromosomes (a.k.a., (a.k.a., homologues)homologues)
SameSame size & shape size & shape Centromere in Centromere in samesame position position SameSame staining characteristics staining characteristics Carry genes for Carry genes for samesame characteristics characteristics
• Karyotype Karyotype PhotomicrographPhotomicrograph of the chromosomes from of the chromosomes from
a dividing cella dividing cell Can be used to determine Can be used to determine genetic defects genetic defects oror
sex of organismsex of organismSex ChromosomesSex Chromosomes
Q: Is this a karyotype of a male or a female?
Karyotyping
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Cell DivisionCell Division
• Cell Division in ProkaryotesCell Division in Prokaryotes
• Cell Division in EukaryotesCell Division in Eukaryotes The Cell CycleThe Cell Cycle InterphaseInterphase MitosisMitosis CytokinesisCytokinesis
LearningLearningObjectivesObjectives
• TSW …TSW …1.1. Describe the events of binary Describe the events of binary
fissionfission
2.2. Describe each phase of the cell Describe each phase of the cell cyclecycle
3.3. Summarize the phases of mitosisSummarize the phases of mitosis
4.4. Compare cytokinesis in plant & Compare cytokinesis in plant & animal cellsanimal cells
Binary FissionBinary FissionNoteNote: no nucleus; no : no nucleus; no mitosismitosis
11 2233
Binary Fission& Asexual Reproduction
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• ASX Video plays about 1 minASX Video plays about 1 min
EukaryoticEukaryoticCell DivisionCell Division
• Mitotic Cell DivisionMitotic Cell Division
OneOne diploid (2n) parent cell diploid (2n) parent cell twotwo diploid (2n) daughter cellsdiploid (2n) daughter cellsGenetic material in daughter cells is Genetic material in daughter cells is
identicalidentical
Occurs in asexual reproduction of Occurs in asexual reproduction of unicellular eukaryotes & addition of new unicellular eukaryotes & addition of new cells to tissues/organscells to tissues/organs
EukaryoticEukaryoticCell DivisionCell Division
• Meiotic Cell DivisionMeiotic Cell Division
OneOne diploid (2n) parent cell diploid (2n) parent cell fourfour diploid (2n) daughter cellsdiploid (2n) daughter cellsGenetic material in daughter cells is NOT Genetic material in daughter cells is NOT
identicalidentical
Occurs in sexual reproduction of Occurs in sexual reproduction of multicellular eukaryotesmulticellular eukaryotes
Mitotic Cell Cycle: Mitotic Cell Cycle: OverviewOverview
• Major StagesMajor Stages of Mitotic Cell of Mitotic Cell Division:Division:―InterphaseInterphase
Divided into Divided into 3 phases3 phases
―Cell DivisionCell Division Mitosis (M phase)Mitosis (M phase)
Division of nucleusDivision of nucleusDivided into Divided into 4-5 main phases4-5 main phases
CytokinesisCytokinesisDivision of cytoplasmDivision of cytoplasm
““mitotic phase” mitotic phase” = division of = division of the cell:the cell:
mitosismitosis
cytokinesiscytokinesis
The Cell Cycle Movie
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• MOV Video plays about 1 minMOV Video plays about 1 min
InterphaseInterphase::Phases of InterphasePhases of Interphase
• Preparatory StagePreparatory Stage:: GG11 phase phase
cell growthcell growth; ; organelles duplicateorganelles duplicate; ; mitochondria & chloroplasts self-replicatemitochondria & chloroplasts self-replicate
S phaseS phaseDNA replicationDNA replication
GG22 phase phaseenzymes & other materialsenzymes & other materials necessary for necessary for
division division synthesizedsynthesized; cell growth ; cell growth continuescontinues
GG00 phasephaseCell exists the cell cycleCell exists the cell cycle; ; organelles organelles duplicateduplicateEX:EX: mature nerve cells of CNS mature nerve cells of CNS
DNA ReplicationDNA Replication
InterphaseInterphase
Interphase
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• MOV Video plays about 25 secMOV Video plays about 25 sec
MitosisMitosis::Phases of MitosisPhases of Mitosis
• PProphaserophase
• MMetaphaseetaphase
• AAnaphasenaphase
• TTelophaseelophase
• ““PPhiladelphia”hiladelphia” or whoever!or whoever!
• MMadeade
• AA
• TTouchdownouchdown
A A
PneumonicPneumonic
Aide!Aide!
Mitosis: ProphaseMitosis: Prophase
• Division of the NucleusDivision of the Nucleus:: Early ProphaseEarly Prophase
chromosomes condensechromosomes condense as sister as sister chromatidschromatids
nucleoli dissolvenucleoli dissolvespindle apparatusspindle apparatus begins to form from begins to form from
centrosomes (centrosomes (MTOCMTOC))
Cytoskeletal Elements of Cytoskeletal Elements of DivisionDivision
• Terminology:Terminology:
CentrosomeCentrosomemicrotubule organizing center (MTOC)microtubule organizing center (MTOC)
synthesizes synthesizes mitoticmitotic spindlespindle
CentriolesCentriolesanimal cells onlyanimal cells only
2/centrosome2/centrosome
9 sets of triplet microtubules arranged in 9 sets of triplet microtubules arranged in ringring
Chromosome & Sister Chromosome & Sister ChromatidsChromatids
Mitosis:Early Prophase
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• MOV Video plays about 20 secMOV Video plays about 20 sec
Mitosis: Late ProphaseMitosis: Late Prophase
• Division of the NucleusDivision of the Nucleus:: Late ProphaseLate Prophase (Prometaphase) (Prometaphase)
nuclear envelope fragmentsnuclear envelope fragmentsspindle stretches across cellspindle stretches across cellspindle microtubules:spindle microtubules:
• Kinetochore fibersKinetochore fibers – some attach to – some attach to chromosomes at kinetochoreschromosomes at kinetochores
• Polar fibersPolar fibers – other microtubules stretch – other microtubules stretch toward poles toward poles
Mitosis:Late Prophase (Prometaphase)
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• MOV Video plays about 20 secMOV Video plays about 20 sec
Mitosis: MetaphaseMitosis: Metaphase
• Division of the NucleusDivision of the Nucleus: : (cont)(cont)
MetaphaseMetaphasespindlespindle across cell w/ centrosomes at across cell w/ centrosomes at
opposite polesopposite poleschromosomes line up acrosschromosomes line up across metaphasemetaphase
plateplate [ [cell equatorcell equator]]• attached to “kinetochore fibers” spindle attached to “kinetochore fibers” spindle
microtubulesmicrotubules• ““polar” microtubules span cell from equator to polar” microtubules span cell from equator to
each poleeach pole
Spindle ApparatusSpindle Apparatus
CentrosomesCentrosomes
centrosomecentrosome
Kinetochore StructureKinetochore Structure
Mitosis:Metaphase
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• MOV Video plays about 12 secMOV Video plays about 12 sec
Mitosis: AnaphaseMitosis: Anaphase
• Division of the NucleusDivision of the Nucleus: : (cont)(cont)
AnaphaseAnaphasecentromeres separatecentromeres separatesister chromatids move to opposite cell sister chromatids move to opposite cell
polespoles as kinetochore fibers as kinetochore fibers shortenshortenPolar fibers Polar fibers lengthenlengthen
Kinetochore FunctionKinetochore Function
Mitosis:Mitosis:AnaphaseAnaphase
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• MOV Video plays about 22 secMOV Video plays about 22 sec
Mitosis:Mitosis:Anaphase Time LapseAnaphase Time Lapse
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• MOV Video plays about 9 secMOV Video plays about 9 sec
Mitosis: Early TelophaseMitosis: Early Telophase
• Division of the NucleusDivision of the Nucleus: : (cont)(cont)
Early TelophaseEarly Telophasepolar fibers polar fibers lengthenlengthen stretching cell stretching cellchromosomes (formerly sister chromosomes (formerly sister
chromatids) reach opposite poles of cellchromatids) reach opposite poles of cell
Mitosis: Late TelophaseMitosis: Late Telophase
• Division of the NucleusDivision of the Nucleus: : (cont)(cont)
Late TelophaseLate Telophasedaughter nuclear envelopes reformdaughter nuclear envelopes reformdaughter nucleoli reformdaughter nucleoli reformchromosomeschromosomes decondensedecondense to to chromatinchromatin
Mitosis:Mitosis:TelophaseTelophase
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• MOV Video plays about 20 secMOV Video plays about 20 sec
CytokinesisCytokinesis
• Division of the CytoplasmDivision of the Cytoplasm:: Begins during Begins during late anaphaselate anaphase to to early early
telophasetelophase Finishes immediately Finishes immediately afterafter telophase telophase Daughter cells separated by different Daughter cells separated by different
mechanisms in plants & animalsmechanisms in plants & animals
CytokinesisCytokinesis
CytokinesisCytokinesis
• Cleavage furrowCleavage furrow formation: formation: animal animal cellscells
microfilaments attached to cell microfilaments attached to cell membrane & shorten to membrane & shorten to pinch cell in pinch cell in twotwo: separating daughter nuclei: separating daughter nuclei
• Cell plateCell plate formation: formation: plant cellsplant cells
vesiclesvesicles produced from produced from Golgi Golgi apparatusapparatus form and fuseform and fuse btw/ btw/ daughter nucleidaughter nuclei
Animal Cell Animal Cell CytokinesisCytokinesis
Cleavage Furrow Cleavage Furrow FormationFormation
Plant Cell Plant Cell CytokinesisCytokinesis
Cell Plate FormationCell Plate Formation
CytokinesisCytokinesis
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• MOV Video plays about 41 secMOV Video plays about 41 sec
Review of Mitosis & Review of Mitosis & CytokinesisCytokinesis
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• MOV Video plays about 30 secMOV Video plays about 30 sec
Mitotic Cell Division:Mitotic Cell Division:Time LapseTime Lapse
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• ASF Video plays about 52 secASF Video plays about 52 sec
Roles of Cell DivisionRoles of Cell Division
• Asexual ReproductionAsexual Reproduction prokaryotesprokaryotes protistansprotistans fungifungi
• Growth & DevelopmentGrowth & Development multicellular organismsmulticellular organisms
• Repair & RegenerationRepair & Regeneration multicellular organismsmulticellular organisms
plantsplants primitive animalsprimitive animals
Asexual ReproductionAsexual Reproduction
ProkaryotesProkaryotes
ProtistansProtistans
PlantsPlants
FungiFungi
Lower AnimalsLower Animalsamoeba amoeba dividingdividing
Asexual ReproductionAsexual Reproduction
cloneclone
Growth & DevelopmentGrowth & Development
Multicellular Multicellular OrganismsOrganisms
Fertilized eggFertilized egg
Ist divisionIst division
Early embryoEarly embryo
Late embryoLate embryo
FetusFetus
ToddlerToddler
Young childYoung child
Young adultYoung adult
DifferentiationDifferentiation
Tissue RenewalTissue Renewal
Multicellular Multicellular OrganismsOrganismsbone marrow bone marrow
stem cellsstem cells
Preservation of the Preservation of the GenomeGenome
The Role of The Role of Mitosis in OrganismsMitosis in Organisms
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• MOV Video plays about 30 secMOV Video plays about 30 sec
Meiotic Cell DivisionMeiotic Cell Division
• Stages of MeiosisStages of Meiosis Meiosis IMeiosis I Meiosis IIMeiosis II
• Formation of GametesFormation of Gametes SpermatogenesisSpermatogenesis OogenesisOogenesis
• Asexual & Sexual ReproductionAsexual & Sexual Reproduction
Learning Learning ObjectivesObjectives
• TSW …TSW …1.1. List & describe the phases of meiosisList & describe the phases of meiosis
2.2. Compare the end products of mitosis Compare the end products of mitosis with those of meiosiswith those of meiosis
3.3. Explain crossing over & discuss how it Explain crossing over & discuss how it contributes to the production of a unique contributes to the production of a unique individualindividual
4.4. Summarize the major characteristics of Summarize the major characteristics of spermatogenesis & oogenesisspermatogenesis & oogenesis
Human KaryotypeHuman Karyotype
NoteNote: 23 pairs of chromosomes = 2 sets: 23 pairs of chromosomes = 2 sets
General Cell TypesGeneral Cell Types
• Germ CellsGerm Cells diploid (2n)diploid (2n) produced during growth & development produced during growth & development
by mitosisby mitosis undergo meiotic cell division to produce undergo meiotic cell division to produce
gametesgametes • Somatic CellsSomatic Cells
diploid (2n)diploid (2n) produced during growth & development produced during growth & development
by mitosisby mitosis all cells of the body all cells of the body exceptexcept for germ cells for germ cells
Overview of Overview of Meiotic Cell DivisionMeiotic Cell Division
Meiotic Cell DivisionMeiotic Cell DivisionMeiosis IMeiosis I
• Interphase – Interphase – preparatory stagepreparatory stage
• Meiosis I – Meiosis I – 11stst nuclear division: nuclear division:
halving of the chromosomehalving of the chromosome numbernumber
• 11stst Cytokinesis – Cytokinesis – division of the division of the cytoplasm: cytoplasm: 2 daughter cells formed2 daughter cells formed
Meiotic Cell Division:Meiotic Cell Division:Meiosis IIMeiosis II
• (Interkinesis) – (Interkinesis) – in some kinds of in some kinds of organisms organisms
• Meiosis II – Meiosis II – 22ndnd nuclear division in both nuclear division in both cells from meiosis I: cells from meiosis I: separation of the separation of the sister chromatidssister chromatids
• 22ndnd Cytokinesis – Cytokinesis – division of the division of the cytoplasm in both cells from meiosis I: cytoplasm in both cells from meiosis I: 4 4 daughter cells formeddaughter cells formed
Meiosis & Meiosis & Chromosome ReductionChromosome Reduction
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• MOV Video plays about 55 secMOV Video plays about 55 sec
InterphaseInterphase::Phases of InterphasePhases of Interphase
• Preparatory StagePreparatory Stage:: GG11 phase phase
cell growthcell growth; ; organelles duplicateorganelles duplicate; ; mitochondria & chloroplasts self-replicatemitochondria & chloroplasts self-replicate
S phaseS phaseDNA replicationDNA replication
GG22 phase phaseenzymes & other materialsenzymes & other materials necessary for necessary for
division produced; cell growth continuesdivision produced; cell growth continues
Meiotic InterphaseMeiotic Interphase
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• MOV Video plays about 20 secMOV Video plays about 20 sec
Meiosis I: Meiosis I: Reduction DivisionReduction Division
• ProphaseProphase I I (includes Prometaphase)(includes Prometaphase) similar to mitosis similar to mitosis exceptexcept: : homologous homologous
chromosomes pair in chromosomes pair in synapsis synapsis to form tetradsto form tetrads
• MetaphaseMetaphase I I similar to mitosis similar to mitosis exceptexcept: : homologs homologs line up line up
across the metaphase plateacross the metaphase plate
• AnaphaseAnaphase I I similar to mitosis similar to mitosis exceptexcept: : homologs are homologs are
separatedseparated to opposite poles of the cell to opposite poles of the cell
• TelophaseTelophase I I similar to mitosis similar to mitosis exceptexcept: : nuclei may or may not nuclei may or may not
reform completelyreform completely
Meiosis I:Meiosis I:ProphaseProphase
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• MOV Video plays about 55 secMOV Video plays about 55 sec
Homologous chromosomesHomologous chromosomes pair pair upup at prophase at prophase
Each homologue has Each homologue has twotwo sister sister chromatids: chromatids: tetradtetrad
The sister chromatids from The sister chromatids from differentdifferent homologues become homologues become tangledtangled:: cross-over cross-over
SynapsisSynapsis
Tetrads & Cross OverTetrads & Cross Over
occurs during occurs during prophase Iprophase I
Meiosis & CrossoverMeiosis & Crossover
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• MOV Video plays about 1 minMOV Video plays about 1 min
Meiosis I:Meiosis I:MetaphaseMetaphase
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• MOV Video plays about 27 secMOV Video plays about 27 sec
Independent AssortmentIndependent Assortment
Homologous chromosomes Homologous chromosomes line up line up independentlyindependently from one another across from one another across the cell equator during metaphasethe cell equator during metaphase
Results of Cross OverResults of Cross Over
Meiosis I:Meiosis I:AnaphaseAnaphase
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• MOV Video plays about 16 secMOV Video plays about 16 sec
Meiosis I:Meiosis I:Telophase & 1st CytokinesisTelophase & 1st Cytokinesis
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• MOV Video plays about 25 secMOV Video plays about 25 sec
11stst Cytokinesis Cytokinesis
• Occurs concurrently with Occurs concurrently with telophase Itelophase I
• Results in 2 daughter cellsResults in 2 daughter cells• Daughter cells contain Daughter cells contain ½ of ½ of
original chromosomesoriginal chromosomes
InterkinesisInterkinesis
• Occurs in Occurs in some speciessome speciesafter telophase I & 1after telophase I & 1stst cytokinesis cytokinesis
• Nuclei of daughter cells completely Nuclei of daughter cells completely reformreform
• Chromosomes –still as joined as Chromosomes –still as joined as sister chromatids – decondensesister chromatids – decondense
• G phases G phases maymay occur; occur; NONO S phase S phase
Meiosis II:Meiosis II:Equational DivisionEquational Division
• ProphaseProphase II II (includes Prometaphase)(includes Prometaphase) • MetaphaseMetaphase II II• AnaphaseAnaphase II II• TelophaseTelophase II II
same processes as mitosis for all same processes as mitosis for all phasesphases
Meiosis IIMeiosis II& 2& 2ndnd Cytokinesis Cytokinesis
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• MOV Video plays about 42 secMOV Video plays about 42 sec
22ndnd Cytokinesis Cytokinesis
• Occurs concurrently with Occurs concurrently with telophase IItelophase II
• Results inResults in 4 daughter cells4 daughter cells• Daughter cells contain Daughter cells contain ½ of ½ of
original chromosomesoriginal chromosomes
DNA Content of CellsDNA Content of Cells
• Original amount of DNA = Original amount of DNA = XX
• After interphase, amnt DNA = After interphase, amnt DNA = 2X2X
• After meiosis I, amnt DNA = After meiosis I, amnt DNA = XX
• After meiosis II, amnt DNA = After meiosis II, amnt DNA = ½ X½ X
Formation of GametesFormation of Gametes
• SpermatogenesisSpermatogenesis Occurs in male germ cellsOccurs in male germ cells Produces sperm Produces sperm
• Oogenesis Oogenesis Occurs in female germ cellsOccurs in female germ cells Produces ova (eggs)Produces ova (eggs)
SpermatogenesisSpermatogenesis
OogenesisOogenesis
Mitosis -v- MeiosisMitosis -v- Meiosis
• Prophase & Prophase & ProphaseProphase I I SynapsisSynapsis of of homologshomologs & chiasmata of non- & chiasmata of non-
sister chromatids in tetradsister chromatids in tetrad
• Metaphase & Metaphase & MetaphaseMetaphase I I HomologsHomologs align at and span metaphase align at and span metaphase
plateplate
• Anaphase & Anaphase & AnaphaseAnaphase I I Homologs separateHomologs separate; ; sister chromatids do sister chromatids do
notnot
Comparison of Comparison of Mitosis & MeiosisMitosis & Meiosis
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• ASX Video plays about 30 minASX Video plays about 30 min
Random FertilizationRandom Fertilization
• With 23 chromosomes, each gamete has With 23 chromosomes, each gamete has 8 million possible chromosome 8 million possible chromosome combinationscombinations
• A zygote can have 8 million (for egg) X 8 A zygote can have 8 million (for egg) X 8 million (for sperm) possible diploid million (for sperm) possible diploid combinations which equals combinations which equals 64 trillion 64 trillion different kinds of individualsdifferent kinds of individuals resulting resulting from one possible matingfrom one possible mating
• This does not take into account variation This does not take into account variation due to cross overdue to cross over!!
Sexual Life Cycles &Sexual Life Cycles &Genetic VariationGenetic Variation
• Sources of Genetic Variation via Sources of Genetic Variation via Sexual ReproductionSexual Reproduction Independent assortmentIndependent assortment of of
chromosomes at metaphase Ichromosomes at metaphase I Cross overCross over Random fertilizationRandom fertilization
The Role of MeiosisThe Role of Meiosis
• Alternation of Fertilization & Alternation of Fertilization & Meiosis:Meiosis: The Human Life CycleThe Human Life Cycle The Variety of Sexual Life The Variety of Sexual Life
CyclesCycles
• Sexual ReproductionSexual Reproduction
Modes of ReproductionModes of Reproduction
• Asexual ReproductionAsexual Reproduction A A single individualsingle individual is the sole parent & is the sole parent &
passes copies of all of its genes to its passes copies of all of its genes to its offspringoffspring
ClonesClones
• Sexual ReproductionSexual Reproduction Two parentsTwo parents give rise to offspring that give rise to offspring that
have have unique combinations of genesunique combinations of genes inherited from both parentsinherited from both parents
Asexual ReproductionAsexual Reproduction
cloneclone
Asexual Life CycleAsexual Life Cycle
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• MOV Video plays about 46 secMOV Video plays about 46 sec
Sexual ReproductionSexual ReproductionIn AnimalsIn Animals
Life Cycles & GametesLife Cycles & Gametes
• Life CycleLife Cycle the generation-to-generation sequence the generation-to-generation sequence
of stages in the reproductive history of of stages in the reproductive history of an organism from conception to an organism from conception to production of its own offspringproduction of its own offspring
• GametesGametes reproductive cellsreproductive cells
eggseggs – from the female – from the femalespermsperm – from the male – from the male
haploidhaploid cells – 1 set of chromosomes; ½ cells – 1 set of chromosomes; ½ chromosome number of adults chromosome number of adults (23 in (23 in humans)humans)
Sexual Reproduction & Sexual Reproduction & DifferentiationDifferentiation
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• ASF Video plays about 3-3/4 minASF Video plays about 3-3/4 min
Typical EukaryoticTypical EukaryoticLife CyclesLife Cycles
alternation of generationsalternation of generations
Fertilization & MeiosisFertilization & Meiosis
• Meiotic Cell DivisionMeiotic Cell Division the production of gametesthe production of gametes reduces thereduces the number of chromosomes number of chromosomes
to ½to ½ that of the adult organism that of the adult organism haploidhaploid cells – 1 set of chromosomes cells – 1 set of chromosomes
(23 in humans)(23 in humans)
Fertilization & MeiosisFertilization & Meiosis
• FertilizationFertilization the union of gametesthe union of gametes results in a results in a diploiddiploid zygotezygote (fertilized (fertilized
egg) that grows and develops via mitosis egg) that grows and develops via mitosis into an adult organisminto an adult organism
diploiddiploid cells – 2 sets of chromosomes cells – 2 sets of chromosomes (46 in humans)(46 in humans)