get ready for a & p! chapter 6 cell biology 1. mid 1600s - robert hooke observed and described...
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Get Ready for A & P!Get Ready for A & P!Chapter 6Chapter 6
Cell BiologyCell Biology
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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
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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
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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
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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?
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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
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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
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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
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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
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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
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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
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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
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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
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Early Prophase - Early Prophase - Mitosis BeginsMitosis Begins
Duplicated chromosomes begin to condenseDuplicated chromosomes begin to condense
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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
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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
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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
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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
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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
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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
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Anaphase IAnaphase I
Homologous Homologous
chromosomes chromosomes
segregatesegregate
The sister The sister
chromatids remain chromatids remain
attachedattached
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Telophase ITelophase I
The chromosomes The chromosomes
arrive at opposite arrive at opposite
polespoles
Usually followed by Usually followed by
cytoplasmic cytoplasmic
divisiondivision
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Prophase IIProphase II
Microtubules attach Microtubules attach to the duplicated to the duplicated chromosomeschromosomes
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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
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Anaphase II Anaphase II
Sister chromatids Sister chromatids separate to separate to become become independent independent chromosomeschromosomes
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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
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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)
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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)
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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
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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
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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
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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
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