Cell Reproduction Chromosomes Cell Division Meiotic Cell Cycle.

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Cell ReproductionCell Reproduction

ChromosomesChromosomes

Cell DivisionCell Division

Meiotic Cell CycleMeiotic Cell Cycle

Mitosis Introduction

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presentationpresentation

• 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

• 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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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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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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MitosisMitosis::Phases of MitosisPhases of Mitosis

• PProphaserophase

• MMetaphaseetaphase

• AAnaphasenaphase

• TTelophaseelophase

• ““PPhiladelphia”hiladelphia” or whoever!or whoever!

• MMadeade

• AA

• TTouchdownouchdown

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

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)

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

Mitosis: AnaphaseMitosis: Anaphase

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

Mitosis:Mitosis:Anaphase Time LapseAnaphase Time Lapse

Mitosis: Early TelophaseMitosis: Early Telophase

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

Late TelophaseLate Telophasedaughter nuclear envelopes reformdaughter nuclear envelopes reformdaughter nucleoli reformdaughter nucleoli reformchromosomeschromosomes decondensedecondense to to chromatinchromatin

Mitosis:Mitosis:TelophaseTelophase

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

• 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

Review of Mitosis & Review of Mitosis & CytokinesisCytokinesis

Mitotic Cell Division:Mitotic Cell Division:Time LapseTime Lapse

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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

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

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

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

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

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

• MOV Video plays about 1 minMOV Video plays about 1 min

Meiosis I:Meiosis I:MetaphaseMetaphase

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

Meiosis I:Meiosis I:Telophase & 1st CytokinesisTelophase & 1st Cytokinesis

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

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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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

cloneclone

Asexual Life CycleAsexual Life Cycle

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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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)

Cell Reproduction Chromosomes Cell Division Meiotic Cell Cycle.

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