Get Ready for A & P!Get Ready for A & P!Chapter 6Chapter 6

Cell BiologyCell Biology

11

Mid 1600s - Robert Hooke observed and Mid 1600s - Robert Hooke observed and

described cells in corkdescribed cells in cork

Late 1600s - Antony van Leeuwenhoek Late 1600s - Antony van Leeuwenhoek

observed sperm, microorganismsobserved sperm, microorganisms

1820s - Robert Brown observed and 1820s - Robert Brown observed and

named nucleus in plant cellsnamed nucleus in plant cells

Early DiscoveriesEarly Discoveries

22

Cell TheoryCell Theory

1) Every organism is composed of one or 1) Every organism is composed of one or

more cellsmore cells

2) Cell is smallest unit having properties of 2) Cell is smallest unit having properties of

lifelife

3) Continuity of life arises from growth and 3) Continuity of life arises from growth and

division of single cellsdivision of single cells

33

Smallest unit of lifeSmallest unit of life

Can survive on its own or has potential to Can survive on its own or has potential to

do sodo so

Is highly organized for metabolismIs highly organized for metabolism

Senses and responds to environmentSenses and responds to environment

Has potential to reproduceHas potential to reproduce

The CellThe Cell

44

Structure of CellsStructure of Cells

All start out life with:All start out life with: Plasma membrane Plasma membrane Region where DNA Region where DNA

is storedis stored Cytoplasm Cytoplasm

Two types:Two types:ProkaryoticProkaryoticEukaryotic Eukaryotic What's the What's the

difference?difference?

55

Prokaryotes v. Eukaryotes

Single cells

No nucleus or

organelles

Smaller, less complex

Single- or multi-Single- or multi-celled celled

Nucleus and Nucleus and other organelles other organelles

Larger, more Larger, more complexcomplex

66

Lipid BilayerLipid Bilayer

Cell membranes consist of a lipid bilayer Cell membranes consist of a lipid bilayer containing different proteinscontaining different proteins

Membrane is a continuous boundary layer Membrane is a continuous boundary layer that selectively controls the flow of that selectively controls the flow of substances across itsubstances across it

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Cell Membranes Show Cell Membranes Show Selective PermeabilitySelective Permeabilityoxygen, carbon dioxide, and other small, nonpolar molecules; some water molecules

glucose and other large, polar, water-soluble molecules; ions (e.g.,H+, Na+, K+, Ca++, Cl–); water molecules

88

Lipid BilayerLipid Bilayer

hydrophilicparts

hydrophobicparts

b

a

fluid

fluid

one layer of lipids

one layer of lipids

cross-sectionthrough lipid bilayer

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Fluid Mosaic ModelFluid Mosaic Model

Every cell membrane has a mixed Every cell membrane has a mixed composition of phospholipids, glycolipids, composition of phospholipids, glycolipids, sterols, and proteinssterols, and proteins

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Fluid Mosaic ModelFluid Mosaic Model

adhesionprotein

cytoskeletal proteins just beneath the plasma

membrane

active transporter(calcium pump)

passivetransporter

active transporter(ATPase pump)

recognitionprotein

receptor

phospholipid

Cytoplasm

PlasmaMembrane

Lipid bilayer

cholesterol

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Animal CellAnimal Cell

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Animal Cell FeaturesAnimal Cell Features

CYTOSKELETON

MITOCHONDRION

CENTRIOLES

LYSOSOME

GOLGI BODY

SMOOTH ER

ROUGH ER

RIBOSOMES

NUCLEUS

PLASMA MEMBRANE

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cytoplasm

nucleus

plasma membrane

nuclear envelope

nucleoplasm

nucleolus

chromatin

NucleusNucleus

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Keeps the DNA molecules of eukaryotic Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery cells separated from metabolic machinery of cytoplasmof cytoplasm

Makes it easier to organize DNA and to Makes it easier to organize DNA and to copy it before parent cells divide into copy it before parent cells divide into daughter cells daughter cells

Functions of NucleusFunctions of Nucleus

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ChromatinChromatin

Cell’s collection of DNA and associated Cell’s collection of DNA and associated proteinsproteins

Chromosome is one DNA molecule and Chromosome is one DNA molecule and its associated proteinsits associated proteins

Appearance changes as cell dividesAppearance changes as cell divides

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NucleolusNucleolus

Dense mass of material in nucleusDense mass of material in nucleus May be one or moreMay be one or more Cluster of DNA and proteinsCluster of DNA and proteins Materials from which ribosomal subunits Materials from which ribosomal subunits

are builtare built Subunits must pass through nuclear pores Subunits must pass through nuclear pores

to reach cytoplasmto reach cytoplasm

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Nuclear EnvelopeNuclear Envelope

Two outer membranes (lipid bilayers)Two outer membranes (lipid bilayers) Pores span bilayer Pores span bilayer

one of two lipid bilayers (facing nucleoplasm)

NUCLEAR ENVELOPE

one of two lipid bilayers (facing nucleoplasm)

nuclear pore (protein complex that spans both lipid bilayers)

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NucleusNucleus

1919

Endoplasmic ReticulumEndoplasmic Reticulum

In animal cells, continuous with nuclear In animal cells, continuous with nuclear

membranemembrane

Extends throughout cytoplasmExtends throughout cytoplasm

Two regions: rough and smoothTwo regions: rough and smooth

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Rough ERRough ER

Arranged into flattened sacsArranged into flattened sacs Ribosomes on surface give it a Ribosomes on surface give it a

rough appearancerough appearance Some polypeptide chains enter Some polypeptide chains enter

rough ER and are modifiedrough ER and are modified Cells that specialize in secreting Cells that specialize in secreting

proteins have lots of rough ERproteins have lots of rough ER

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Smooth ERSmooth ER

A series of interconnected A series of interconnected tubules tubules

No ribosomes on surfaceNo ribosomes on surface Lipids assembled inside Lipids assembled inside

tubulestubules Smooth ER of liver inactivates Smooth ER of liver inactivates

wastes, drugswastes, drugs Sarcoplasmic reticulum of Sarcoplasmic reticulum of

muscle is a specialized formmuscle is a specialized form2222

Golgi BodiesGolgi Bodies

Put finishing touches on proteins Put finishing touches on proteins and lipids that arrive from ERand lipids that arrive from ER

Package finished material for Package finished material for shipment to final destinationsshipment to final destinations

Material arrives and leaves in Material arrives and leaves in vesiclesvesicles

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MitochondriaMitochondria

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ATP-producing powerhousesATP-producing powerhouses

Double-membrane system Double-membrane system

Carry out the most efficient Carry out the most efficient

energy-releasing reactionsenergy-releasing reactions

These reactions require oxygenThese reactions require oxygen

MitochondriaMitochondria

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VesiclesVesicles

Membranous sacs that move through Membranous sacs that move through

the cytoplasmthe cytoplasm

Lysosomes – digestive enzymesLysosomes – digestive enzymes

Peroxisomes – detoxifying chemicalsPeroxisomes – detoxifying chemicals

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Flagella and CiliaFlagella and Cilia

Structures Structures

for cell for cell

motilitymotility

Cilia – Cilia –

many, shortmany, short

Flagella – Flagella –

few, longfew, long

plasmamembrane

basal body (embedded in the cytoplasm)

plasmamembrane

microtubules near base of flagellum or cilium

one of nine pairs of microtubules withdynein arms down their length

spokes, rings of connective system

centralsheath

one central pairof microtubules

2727

CiliaCilia

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FlagellumFlagellum

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Concentration Gradient Concentration Gradient

Means the number of molecules or ions in Means the number of molecules or ions in one region is different than the number in one region is different than the number in another regionanother region

In the absence of other forces, a In the absence of other forces, a substance moves from a region where it is substance moves from a region where it is more concentrated to one where it’s less more concentrated to one where it’s less concentrated - “down” gradientconcentrated - “down” gradient

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Membrane Crossing Membrane Crossing MechanismsMechanisms

Diffusion across lipid bilayerDiffusion across lipid bilayer

Passive transportPassive transport

Active transportActive transport

EndocytosisEndocytosis

ExocytosisExocytosis

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DiffusionDiffusion The net movement of like molecules or The net movement of like molecules or

ions ions down a concentration gradientdown a concentration gradient Although molecules collide randomly, the Although molecules collide randomly, the

net movement is away from the place with net movement is away from the place with the most collisions (down gradient)the most collisions (down gradient)

When molecules are large and moving When molecules are large and moving through a membrane, they sometimes through a membrane, they sometimes must be helped across by a membrane must be helped across by a membrane protein. This process is called protein. This process is called facilitated facilitated diffusion.diffusion.

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DiffusionDiffusion

Stepped Art

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Factors Affecting Factors Affecting Diffusion RateDiffusion Rate

Steepness of concentration gradientSteepness of concentration gradient Steeper gradient, faster diffusionSteeper gradient, faster diffusion

Molecular sizeMolecular size Smaller molecules, faster diffusionSmaller molecules, faster diffusion

TemperatureTemperature Higher temperature, faster diffusionHigher temperature, faster diffusion

Electrical or pressure gradientsElectrical or pressure gradients Opposite charges, higher pressure, faster diffusionOpposite charges, higher pressure, faster diffusion

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Osmosis Osmosis

Diffusion of water molecules across a Diffusion of water molecules across a selectively permeable membraneselectively permeable membrane

water molecules protein molecules

semipermeable membranebetween two compartments

• Direction of net flow is determined by water concentration gradient

• Side with the most solute molecules has the lowest water concentration

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Tonicity Tonicity

Refers to Refers to relativerelative solute concentration of solute concentration of two fluidstwo fluids

Hypotonic - having fewer solutesHypotonic - having fewer solutes

Hypertonic - having more solutes Hypertonic - having more solutes

Isotonic - having same amountIsotonic - having same amount

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2% sucrose solution

1 liter of distilled water

1 liter of 10% sucrose

solution

1 liter of 2% sucrose

solution

HypotonicConditions

HypertonicConditions

IsotonicConditions

Tonicity and Tonicity and OsmosisOsmosis

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Passive Transport Passive Transport

Flow of solutes through the interior of Flow of solutes through the interior of passive transport proteins down their passive transport proteins down their concentration gradientsconcentration gradients

Passive transport proteins allow solutes to Passive transport proteins allow solutes to move both ways (facilitated diffusion)move both ways (facilitated diffusion)

Does not require any energy inputDoes not require any energy input

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Passive TransportPassive Transport

Stepped Art

glucose transporter

solute (glucose)

high

low

3939

Active TransportActive Transport

Net diffusion of solute is against Net diffusion of solute is against concentration gradient – takes energyconcentration gradient – takes energy

Transport protein must be activatedTransport protein must be activated ATP gives up phosphate to activate ATP gives up phosphate to activate

proteinprotein Binding of ATP changes protein shape Binding of ATP changes protein shape

and affinity for soluteand affinity for solute

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Endocytosis and ExocytosisEndocytosis and Exocytosis

ExocytosisExocytosis: A cytoplasmic vesicle fuses : A cytoplasmic vesicle fuses with the plasma membrane and contents with the plasma membrane and contents are released outside the cellare released outside the cell

EndocytosisEndocytosis: A small patch of plasma : A small patch of plasma membrane sinks inward and seals back on membrane sinks inward and seals back on itself, forming a vesicle inside the itself, forming a vesicle inside the cytoplasm – membrane receptors often cytoplasm – membrane receptors often mediate this processmediate this process

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endocytosis exocytosis

coated pit

a

b

d c

ef

Endocytosis Endocytosis and and

ExocytosisExocytosis

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Watson-Crick ModelWatson-Crick Model

DNA consists of two nucleotide strandsDNA consists of two nucleotide strands

Strands run in opposite directionsStrands run in opposite directions

Strands are held together by hydrogen Strands are held together by hydrogen

bonds between basesbonds between bases

A binds with T and C with GA binds with T and C with G

Molecule is a double helixMolecule is a double helix

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DNA Structure Helps DNA Structure Helps Explain How It DuplicatesExplain How It Duplicates

DNA is two nucleotide strands held DNA is two nucleotide strands held

together by hydrogen bondstogether by hydrogen bonds

Hydrogen bonds between two strands Hydrogen bonds between two strands

are easily brokenare easily broken

Each single strand then serves as Each single strand then serves as

template for new strandtemplate for new strand4444

DNA DNA ReplicationReplication

Each parent Each parent

strand remains strand remains

intactintact

Every DNA Every DNA

molecule is half molecule is half

“old” and half “old” and half

“new”“new”45

Base Pairing Base Pairing during during

ReplicationReplication

Each old strand Each old strand serves as the serves as the template for template for complementary complementary new strandnew strand

4646

a A parent DNA molecule with two complementary strands of base-paired nucleotides.

b Replication starts; the strands unwind and move apart from each other at specific sites along the molecule’s length.

c Each “old” strand is a structural pattern (template) for attaching new bases, according to the base-pairing rule.

d Bases positioned on each old strand are joined together as a “new” strand. Each half-old, half-new DNA molecule is like the parent molecule. 4747

ReproductionReproduction

Parents produce a new generation of cells Parents produce a new generation of cells or multicelled individuals like themselvesor multicelled individuals like themselves

Parents must provide daughter cells with Parents must provide daughter cells with hereditary instructions, encoded in DNA, hereditary instructions, encoded in DNA, and enough metabolic machinery to start and enough metabolic machinery to start up their own operationup their own operation

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Division Mechanisms Division Mechanisms

Eukaryotic organisms Eukaryotic organisms

MitosisMitosis

MeiosisMeiosis

Prokaryotic organismsProkaryotic organisms

Prokaryotic fissionProkaryotic fission

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Roles of MitosisRoles of Mitosis

Multicelled organismsMulticelled organisms

GrowthGrowth

Cell replacementCell replacement

Some protistans, fungi, plants, animalsSome protistans, fungi, plants, animals

Asexual reproductionAsexual reproduction

5050

a One chromosome (unduplicated)

b One chromosome (duplicated)

one chromatid two sister chromatidsone chromatid

Stepped Art

ChromosomeChromosome A DNA molecule & attached proteinsA DNA molecule & attached proteins Duplicated in preparation for mitosisDuplicated in preparation for mitosis

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Chromosome Number Chromosome Number

Sum total of chromosomes in a cell Sum total of chromosomes in a cell Somatic cellsSomatic cells

Chromosome number is diploid (2Chromosome number is diploid (2nn)) Two of each type of chromosomeTwo of each type of chromosome

GametesGametes Chromosome number is haploid (Chromosome number is haploid (nn)) One of each chromosome typeOne of each chromosome type

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Human Chromosome NumberHuman Chromosome Number

Diploid chromosome number (Diploid chromosome number (nn) = 46) = 46

Two sets of 23 chromosomes eachTwo sets of 23 chromosomes each One set from fatherOne set from father One set from motherOne set from mother

Mitosis produces cells with 46 Mitosis produces cells with 46 chromosomes - two of each typechromosomes - two of each type

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Maintaining Maintaining Chromosome Chromosome

NumberNumber

mitosis, cytoplasmic divisionchromosome (unduplicated) in daughter cell at interphase

chromosome (unduplicated) in daughter cell at interphase

chromosome (unduplicated) in cell at interphase

same chromosome (duplicated) in interphase prior to mitosis

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InterphaseInterphase

Usually longest part of the cycleUsually longest part of the cycle

Cell increases in massCell increases in mass

Number of cytoplasmic components Number of cytoplasmic components

doublesdoubles

DNA is duplicatedDNA is duplicated

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Mitosis Mitosis

Period of nuclear divisionPeriod of nuclear division Usually followed by cytoplasmic divisionUsually followed by cytoplasmic division Four stages:Four stages:

ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophase

5656

Early Prophase - Early Prophase - Mitosis BeginsMitosis Begins

Duplicated chromosomes begin to condenseDuplicated chromosomes begin to condense

5757

Late ProphaseLate Prophase

New microtubules are New microtubules are assembledassembled

One centriole pair is One centriole pair is moved toward opposite moved toward opposite pole of spindlepole of spindle

Nuclear envelope starts Nuclear envelope starts to break upto break up

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The Spindle ApparatusThe Spindle Apparatus

Consists of two distinct sets of Consists of two distinct sets of

microtubulesmicrotubules

Each set extends from one of the cell polesEach set extends from one of the cell poles

Two sets overlap at spindle equatorTwo sets overlap at spindle equator

Moves chromosomes during mitosisMoves chromosomes during mitosis

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Spindle ApparatusSpindle Apparatus

one spindle pole

one of the condensed chromosomes

spindle equator

microtubules organized as a spindle apparatus

one spindle pole

6060

Transition to MetaphaseTransition to Metaphase

Spindle formsSpindle forms Spindle Spindle

microtubules microtubules become attached to become attached to the two sister the two sister chromatids of each chromatids of each chromosomechromosome

6161

MetaphaseMetaphase

All chromosomes All chromosomes are lined up at the are lined up at the spindle equatorspindle equator

Chromosomes are Chromosomes are maximally maximally condensedcondensed

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AnaphaseAnaphase

Sister chromatids Sister chromatids of each of each chromosome are chromosome are pulled apartpulled apart

Once separated, Once separated, each chromatid is a each chromatid is a chromosome chromosome

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TelophaseTelophase

Chromosomes Chromosomes decondensedecondense

Two nuclear Two nuclear membranes form, membranes form, one around each set one around each set of unduplicated of unduplicated chromosomeschromosomes

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Results of MitosisResults of Mitosis

Two daughter nuclei Two daughter nuclei Each with same Each with same

chromosome chromosome number as parent number as parent cellcell

Chromosomes in Chromosomes in unduplicated formunduplicated form

6565

Cytoplasmic Division Cytoplasmic Division

Usually occurs between late anaphase Usually occurs between late anaphase

and end of telophaseand end of telophase

Two mechanisms Two mechanisms

Cell plate formation (plants)Cell plate formation (plants)

Cleavage (animals)Cleavage (animals)

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Animal Cell DivisionAnimal Cell Division

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Sexual ReproductionSexual Reproduction

Chromosomes are duplicated in germ cellsChromosomes are duplicated in germ cells Germ cells undergo meiosis and Germ cells undergo meiosis and

cytoplasmic divisioncytoplasmic division Cellular descendents of germ cells Cellular descendents of germ cells

become gametesbecome gametes Gametes meet at fertilizationGametes meet at fertilization

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Sexual ReproductionSexual Reproduction

InvolvesInvolves

MeiosisMeiosis

Gamete productionGamete production

FertilizationFertilization Produces genetic variation among Produces genetic variation among

offspringoffspring

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Gamete FormationGamete Formation

Gametes are sex cells (sperm, eggs)Gametes are sex cells (sperm, eggs) Arise from germ cellsArise from germ cells

testes

ovaries

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Meiosis: Two DivisionsMeiosis: Two Divisions

Two consecutive nuclear divisions Two consecutive nuclear divisions Meiosis IMeiosis I

Meiosis IIMeiosis II

DNA is not duplicated between divisionsDNA is not duplicated between divisions

Four haploid nuclei formFour haploid nuclei form

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Meiosis I - StagesMeiosis I - Stages

Prophase I Metaphase I Anaphase I Telophase I

7272

Prophase IProphase I

Each duplicated Each duplicated chromosome pairs with chromosome pairs with homologuehomologue

Homologues swap Homologues swap segmentssegments

Each chromosome Each chromosome becomes attached to becomes attached to spindlespindle

7373

Metaphase IMetaphase I

Chromosomes are Chromosomes are pushed and pulled pushed and pulled into the middle of into the middle of cellcell

The spindle is fully The spindle is fully formedformed

7474

Anaphase IAnaphase I

Homologous Homologous

chromosomes chromosomes

segregatesegregate

The sister The sister

chromatids remain chromatids remain

attachedattached

7575

Telophase ITelophase I

The chromosomes The chromosomes

arrive at opposite arrive at opposite

polespoles

Usually followed by Usually followed by

cytoplasmic cytoplasmic

divisiondivision

7676

Prophase IIProphase II

Microtubules attach Microtubules attach to the duplicated to the duplicated chromosomeschromosomes

7777

Metaphase IIMetaphase II

Duplicated Duplicated chromosomes line chromosomes line up at the spindle up at the spindle equator, midway equator, midway between the polesbetween the poles

7878

Anaphase II Anaphase II

Sister chromatids Sister chromatids separate to separate to become become independent independent chromosomeschromosomes

7979

Telophase II Telophase II

The chromosomes The chromosomes arrive at opposite arrive at opposite ends of the cellends of the cell

A nuclear envelope A nuclear envelope forms around each forms around each set of set of chromosomeschromosomes

Four haploid cellsFour haploid cells

8080

SpermatogenesisSpermatogenesis

GrowthMeiosis I,

Cytoplasmic DivisionMeiosis II,

Cytoplasmic Division

cell differentiation, sperm formation

spermatids (haploid)

secondary spermatocytes

(haploid)

primary spermatocyte

(diploid)

spermato-gonium (diploid )

sperm (mature, haploid male

gametes)

8181

OogenesisOogenesis

GrowthMeiosis I,

Cytoplasmic DivisionMeiosis II,

Cytoplasmic Division

ovum (haploid)

primary oocyte (diploid)

oogonium (diploid)

secondary oocyte

(haploid)

first polar body

(haploid)

three polar bodies

(haploid)

8282

MitosisMitosis FunctionsFunctions

Asexual reproductionAsexual reproduction Growth, repair Growth, repair

Occurs in somatic Occurs in somatic cellscells

Produces clonesProduces clones

Mitosis & Meiosis ComparedMitosis & Meiosis Compared

MeiosisMeiosis Function Function

Sexual reproductionSexual reproduction

Occurs in germ cellsOccurs in germ cells

Produces variable Produces variable offspringoffspring

8383

Prophase vs. Prophase I Prophase vs. Prophase I

Prophase (Mitosis)Prophase (Mitosis) Homologous pairs do not interact with each Homologous pairs do not interact with each

otherother

Prophase I (Meiosis) Prophase I (Meiosis) Homologous pairs become zippered together Homologous pairs become zippered together

and crossing over occursand crossing over occurs

8484

Anaphase, Anaphase I, and Anaphase, Anaphase I, and Anaphase IIAnaphase II

Anaphase I (Meiosis)Anaphase I (Meiosis)

Homologous chromosomes separate from Homologous chromosomes separate from

each othereach other

Anaphase/Anaphase II (Mitosis/Meiosis)Anaphase/Anaphase II (Mitosis/Meiosis)

Sister chromatids of a chromosome separate Sister chromatids of a chromosome separate

from each otherfrom each other

8585

Results of Mitosis and MeiosisResults of Mitosis and Meiosis

MitosisMitosis Two diploid cells producedTwo diploid cells produced

Each identical to parentEach identical to parent

MeiosisMeiosis Four haploid cells producedFour haploid cells produced

Differ from parent and one anotherDiffer from parent and one another

8686