Todays Plan: 1/18/11Bellwork: Go over Test (20 mins)Cell Microscopy Lab(40 mins)Cells Notes (25 mins)

Todays Plan: 1/19/11Bellwork: Finish Microscopy (20 mins)Begin AP Lab 1 (40 mins)Cells Notes (the rest of class)

Cells NotesInside the black boxUntil the advent of the electron microscope, only the nucleus and membrane were knownChemical analysis and cell fractionation gave us some clue as to the chemical make up of cells, but thats only part of the pictureThe human eye is unable to detect things smaller than .1mmEukaryotic cells range from 10-100 micrometersProkaryotic cells run from 1-10 micrometers, but the smallest are almost 100 nmMost cellular organelles are about the size of bacteria, however, a few, like the ribosome, are smaller still

2 Main Cell TypesProkaryotesNo nucleus or membrane-bound organellesHas a region called the nucleoid for its genetic materialOnly Archaebacteria and Eubacteria are prokaryoticEukaryotesHave a nucleus and an array of membrane-bound organellesBecause of the membrane system, cell parts are compartmentalized and division of labor is more efficient

Figure 7-1RibosomesPlasmidsFlagellumCell wallPlasmamembraneChromosomeCytoplasm

Figure 7-6aGeneralized animal cellCentriolesNuclear envelopeNucleolusChromosomesNucleusRough endoplasmicreticulumRibosomesPeroxisomeSmooth endoplasmicreticulumGolgi apparatusLysosomeMitochondrionCytoskeletal elementPlasma membraneStructures thatoccur in animal cellsbut not plant cells

Figure 7-6bGeneralized plant cellCell wallChloroplastCytoskeletal elementPlasma membraneMitochondrionPeroxisomeVacuole (lysosome)Golgi apparatusSmooth endoplasmicreticulumRibosomesRough endoplasmicreticulumChromosomesNucleolusNuclear envelopeNucleusStructures thatoccur in plant cellsbut not animal cellsOn average, prokaryotes are about 10times smaller than eukaryotic cells indiameter and about 1000 times smallerthan eukaryotic cells in volume.

Todays Plan: 1/15/10Bellwork: Set up Dialysis Tubes (25 mins)Continue with Cells notes/Finish Microscopy lab (40 mins)Finish Dialysis Tubes (20 mins)

NucleusContains the genes responsible for cell function (chromatin-uncoiled, tangled, DNA mass)Contains Nucleolus which makes the ribosomesNuclear pores in the nuclear envelope allow RNA and ribosomes to pass to the cytoplasm for making proteinsFree ribosomes usually make proteins to be used within the cytoplasmBound ribosomes usually make proteins that need packagingNuclear envelope is lined with the nuclear lamina-a network of proteins that help the nucleus maintain its shape

Figure 7-7Looselypacked sectionsof chromosomesDenselypacked sectionsof chromosomesNucleolusNuclear envelopeNucleus

Figure 7-23Outer surfaceof nuclearenvelopeNuclear pores

The Endomembrane SystemEndoplasmic Reticulum (ER)Vast network of membrane and sacs called cisternaeConsists of approximately of the totalmembrane of the cellSmooth=no bound ribosomes, synthesizes lipids, metabolizes glucose and detoxifies drugs/poisonsRough=bound ribosomes, which thread the emerging proteins that they make through the cisternal space into the ERTransitional=budding area where secretory proteins are sent in transport vesicles to the Golgi apparatus

Figure 7-9Lumen ofrough ERRibosomeson outsideof rough ERFreeribosomesin cytoplasmRough endoplasmicreticulum

Golgi ApparatusPart of the endomembrane system that consists of flattened membranous sacsWharehouses, sorts, modifies, packages, and ships the products of the ERPolarity exists because of the 1-way movement through the cisternae as ER products pass from the cis pole to the trans pole of the sac

Figure 7-10VesicleLumen of GolgiapparatusCisternaeVesiclesThe cis face of the Golgi apparatusis oriented towards the rough ERThe trans face of the Golgi apparatusis oriented towards the plasmamembrane Golgi apparatustrans facecis face

Figure 7-26THE SECRETORY PATHWAY: A MODELRNARough ERGolgi apparatuscis face ofGolgi apparatustrans face ofGolgi apparatusPlasma membrane1. Protein entersER while beingsynthesized byribosome.2. Protein exits ER,travels to cis faceof Golgi apparatus.3. Protein entersGolgi apparatus andis processed as thecisternum movestoward the trans face.4. Protein exits Golgiapparatus at transface and moves toplasma membrane.5. Protein issecreted from cell.

Todays Plan: 1/19/10Bellwork: Set up potatoes (20 mins)Do Lab Part E and finish Microscopy (40 mins)Plasma Membrane notes (25 mins)

Lysosomes and VacuolesLysosomes are sacs for storage of hydrolytic enzymesThese enzymes work best in an acidic environment, so H+ are pumped into the lysosomeCan digest external elements that are brought into the cell or can digest old, worn-out cell componentsPompes disease-occurs when a persons lysosomes lack an enzyme for metabolizing glycogen, which builds upTay-Sachs disease-occurs when lysosomes lack a lipid-digesting enzyme and causes brain impairmentVacuoles are membrane sacs for general storageFood vacuolesContractile vacuoles (pump water out of the cell)Central vacuole (in plants) is surrounded by membrane called the tonoplast-part of the plants endomembrane system

Figure 7-13Material beingdigested withinlysosomesLysosomes

Figure 7-16VacuoleVacuole

Other membrane-bound organellesMitochondriaGenerates ATP during the last 2 stages of aerobic cellular respirationConsists of 2 membranes. The inner membrane is folded into cristae, and inside is called the matrix2 membranes form the intermembrane space Chloroplasts (and other plastids)Contains membranous discs called thylakoids that are stacked into grana-chlorophyll is embedded on the thylakoid membranesContains fluid called stroma that surrounds the thylakoidsOther plastids store pigments or starch (amyloplasts)PeroxisomeSingle membrane-bound organelle that contain enzymes which transfer hydrogen to oxygen, making Hydrogen peroxideAlso contains enzymes that convert the peroxide to water since the peroxide is toxic to the cell

Figure 7-17Outerand innermembranesMatrixCristaeMitochondrion

Figure 7-18StromaThylakoidsGranumOuter and innermembranesChloroplast

Figure 7-12PeroxisomemembranePeroxisomelumenPeroxisomes

CytoskeletonSupports and gives structure to the cellAlso involved in movement (cilia and flagella)Can act as a monorail for the organelles to move around the cellConsists of proteins Microtubules (thickest)-hollow, walls made of tubulin molecules, grow from centrosome (near nucleus) to also form the centrioles for cell divisionMicrofilaments (thinnest)-twisted actin molecules, in muscle cells are paired with myosin filaments for contractionIntermediate filaments-fibrous proteins supercoiled, make up nuclear lamella, and support long extensions of the cell

Figure 7-30-Table 7-3

Figure 7-31Actin filaments in mammalian cellIntermediate filaments in mammalian cellMicrotubules in mammalian cell

Cell SurfacesCell Wall-Plant Cells onlyMade of cellulosePrimary cell wall-thin, flexible, secreted in young plant cells (outermost cell surface)Middle Lamella-sticky layer between primary cell walls of adjacent plant cells (contains pectin)Secondary Cell wall-laid down by older plant cells between the p.m. and primary cell wall. This is much thicker, and usually consists of several layersExtracellular Matrix-Animal Cells onlyNetwork of glycoproteins (like collagen) and proteoglycans (another type of glycoprotein thats thinner and contain more carbohydrate than the typical glycoprotein) which connect to fibronectins and integrins that connect directly to the cytoskeleton.This allows changes on the outside of the cell to be transmitted to the inside of the cell and vice-versa, which allows for regulation of the cells behavior

Figure 7-19Plasmamembraneof cell 1Plasmamembraneof cell 2Cytoplasmof cell 1Cell wallof cell 1Cell wallof cell 2Cytoplasmof cell 2Cell wall

Figure 8-5ECMGel-formingpolysaccharidesIntegrinFibronectinCollagenPlasmamembraneCytoskeletonActin filament

Figure 8-43 chainsCollagen fibrilsrunning lengthwiseCollagen moleculeCollagen fibrils in the extracellular matrix Cell in connective tissueCollagen fibrilsin cross sectionEach collagen fibril iscomposed of manycollagen moleculesCollagen molecules are made of three chains that windaround each other.1.5 nm

Todays Plan:1/20/10Bellwork: Finish Lab 1 (20 mins)Begin Lab 3 (30 mins)Continue Notes (30 mins)

Cell JunctionsIn plants, the cell walls have plasmodesmata to allow for cytoplasmic exchange between cells.Animal cells have 3 main junctionsTight junction-membranes are fused, forms a seal (useful in intestines)Desmosomes-intermediate fillaments transect neighboring membranes, acting like bolts to hold cells togetherGap Junction-Proteinaceous pores between membranes allowing for cytoplasmic exchangeWhy different junctions?There are situations where strength is integral, however there are other situations where cells must chemically communicate, requiring flow between membranes

Figure 8-14Plasmodesmata create gaps that connect plant cells.Tubule ofendoplasmicreticulum passing throughplasmodesmataGap junctions create gaps that connect animal cells.Gapjunctions Membrane proteinsfrom adjacent cellsline up to forma channelMembraneof cell 1Cell wallsSmoothendoplasmicreticulumMembraneof cell 2Cell wallof cell 1Cell wallof cell 2

Figure 8-10Three-dimensional view of a tight junctionMembrane proteins thatform a tight junctionPlasma membranesof adjacent cellsElectron micrograph of a tight junctionA tight junction forms awatertight seal betweenepithelial cellsTight junction

Figure 8-113-D view of desmosomePlasma membranesof adjacent cellsDesmosomeMicrograph of desmosomeAnchoringproteinsinside cellMembraneproteins thatlink cellsIntermediatefilaments

Plasma Membrane StructureRecall that phospholipids are the basic membrane moleculesThey contain a phosphate (hydrophilic) and 2 fatty acid tails (hydrophobic)-amphipathicThey form bilayers so that the lipid tails are always isolated from water.Chemical analysis reveals that proteins are present as well. It was originally believed that the proteins coated the inner and outer surfaces of the P.M.However our current understanding is that proteins of the plasma membrane also have hydrophobic and hydrophilic regions, and therefore transect the P.M

Figure 6-4bPhospholipidPolar head(hydrophilic)Nonpolar tail(hydrophobic)

Figure 6-5Lipid micellesLipid bilayersWaterNo waterHydrophilic heads interact with waterHydrophobic tails interact with each otherHydrophilic heads interact with water

The Fluid Mosaic Model of the P.M.Phospholipids within the P.M. arent static, they shift laterally past one another because the interactions of these molecules are weaker than covalent bonds-FluidProteins appear to be directed by the cytoskeleton below the PMBesides phospholipids and proteins, cholesterol is embedded in the membrane-MosaicThis lends stability to the membrane by reducing the fluid nature of the membrane at high temps and keeps the phospholipids from compacting at low temperatures and solidifying-this would reduce its permeability

Figure 6-10Lipid bilayer withno unsaturatedfatty acidsLipid bilayer withmany unsaturatedfatty acidsLower permeabilityHigher permeability

Figure 6-13Phospholipids arein constant lateralmotion, but rarelyflip to the otherside of the bilayer

Membrane ProteinsIntegral proteins (embedded)Transect the membrane (either entirely or partially)Peripheral proteinsBound loosely to the surface of the PM (or embedded proteins)On inner surface, can be bound to cytoskeletonOn outer surface, can be bound to the ECM

Figure 6-20Outside cellInside cellPeripheralmembraneproteinIntegralmembraneproteinPeripheralmembraneprotein

Todays Plan: 1/21/10Finish Membrane Notes (20 mins)Finish Part I of Lab 3(30 mins)Finish notes on cell cycle(30 mins)

Membrane FunctionsTransport-to maintain homeostasisEnzymatic activity-enzymes embedded in membranes that do metabolic processes (ATP synthase)Signal transduction-a binding site on a receptor protein may chemically change when bound, transmitting the signal to the inside of the cellIntercellular joining-proteins link together cells (desmosomes)Recognition-glycoproteins on cell surfaces may bind to sites on adjacent membrane proteins so that the cells may recognize one anotherAttachment to the cytoskeleton and ECM-can allow for coordination between the two

Transport across membranesHydrophobic core-Barrier for most polar substances (except very small ones like water and ethanol)Does not inhibit hydrophobic molecules like oxygen gas, carbon dioxide, and hydrocarbonsWhatever cant get in through the membrane, must somehow use a protein to get in (either by pump or channel with a hydrophilic tube in the center)

Concentration and transport RulesConcentration gradient=Diffusion rule= particles move from ____ to ____ concentration until they reach __________ ______________ (movement with a concentration gradient)Osmosis=Passive=Active=Water always moves to the _______ _______ because _______________.

Figure 6-15OSMOSIS1. Start with more soluteon one side of the lipidbilayer than the other,using molecules thatcannot cross theselectively permeablemembrane.2. Water undergoes a netmovement from the regionof low concentration ofsolute to the region ofhigh concentration.

Concentration descriptorsHypertonic solutions=Hypotonic solutions=Isotonic solutions=Remember, Hypotonic and hypertonic work in pairs! If the cells environment is hypotonic to the cell, than the cell is hypertonic to the environment (and vice-versa)

Figure 6-16Hypertonic solutionIsotonic solutionHypotonic solutionNet flow of water out of cell; cell shrinksNet flow of water into cell;cell swells or even burstsNo change

OsmoregulationCells have to constantly regulate water uptake and loss or there are consequences (particularly animal cells)Lysis occurs if too much water flows in (some cells have contractile vacuoles to cope with this)Shrivelling and dehydration occur if too much water is lost from the cell (plasmolysis in plant cells occurs when this happens and the PM pulls away from the cell wall)

Protein-Facilitated DiffusionSome proteins can change shape (enzyme-style) when molecules that need transport bind to specific sitesThis is done with a concentration gradient and therefore requires no energy

Figure 6-25bPotassium channels allow only potassium ions to passthrough.Outside cellInside cellClosedOpenPotassium ions can enter thechannel, but cannot pass into the cellWhen a change in electrical charge occursoutside the membrane, the protein changesshape and allows the ions to pass through

Active TransportGoes against a concentration gradientTherefore requires energyEx: Sodium/Potassium Pump

Figure 6-28-1HOW THE SODIUM-POTASSIUM PUMP (Na+/K+- ATPase) WORKS Outsidecell Insidecell Phosphategroup 1. Three binding sites withinthe protein have a highaffinity for sodium ions. 2. Three sodium ions fromthe inside of the cell bind tothese sites. 3. A phosphate group fromATP binds to the protein.In response, the proteinchanges shape. 4. The sodium ions leavethe protein and diffuse tothe exterior of the cell.

Figure 6-28-25. In this conformation, theprotein has binding sites witha high affinity for potassiumions. HOW THE SODIUM-POTASSIUM PUMP (Na+/K+- ATPase) WORKS 6. Two potassium ions bindto the pump. 7. The phosphate group dropsoff the protein. In response,the protein changes back toits original shape. 8. The potassium ions leavethe protein and diffuse to theinterior of the cell. These 8steps repeat.

Figure 6-29Diffusion Facilitated diffusion Active transport Outsidecell Insidecell Passive movement of small,uncharged molecules alongan electrochemical gradient,through a membranePassive movement of Active movement of

Cell CommunicationIs believed to have evolved in prokaryotes and single-celled eukaryotesIn single-celled organisms, the primary purpose of signaling is to induce conjugationThis has become a useful process for multicellular organisms, which have evolved the ability to do long-distance signalingLocal regulators-travel short distances from the cellSynaptic signaling-between nerve cellsHormonal signalingCell junction signaling and cell recognition (as discussed before)

The 3 Stages of Cell SignalingReceptionSignal is detected when it binds to a receptor protein on the cells surfaceTransductionThe surface binding causes a change in the integral protein which initiates transduction inside the cell (can be 1-step, but more often involves multiple steps in a biochemical pathway)ResponseThe signal triggers a cells responseEx:Lactose present in the body needs lactase to break it down

Figure 8-17Cell activity changesReceptorproteinin membraneInside of cellIntracellularsignalOutside of cellIntercellularsignalOVERVIEW OF SIGNAL TRANSDUCTION PATHWAYFor example, specific genes or proteins are activated or deactivated.1. Signal is received.2. Signal is transduced.3. Signal is amplified.4. Cell responds.

ReceptorsJust as with enzymes, the signaling molecule and receptor shape must be complimentaryLigand=molecule that specifically binds to another moleculeThis ligand binding generally causes a change in the shape of the protein receptor, enabling it to react with other cellular moleculesSome receptors are found within the cell, so the signal molecule has to pass through the membrane to dock with the receptor (ex: testosterone)

Figure 8-18SubstrateSignalG protein in offconformationHOW DO G PROTEINS WORK?ReceptorEnzymeGDPGTPG protein in onconformationSecond messengerTriggers responseEnzymeGTP1. G protein binds GDP. Signalarrives and binds to receptor.2. Signal-receptor complex changesconformation. G protein binds GTPand splits into two parts.3. In response to binding of activatedG protein, enzyme catalyzes areaction that produces a secondmessenger.

Figure 8-16PlasmamembraneSteroidhormoneTarget gene DNAReceptorin cytosolNucleusSTEROID HORMONES BIND TO SIGNAL RECEPTORS INSIDE THE CELL.1. Steroid hormonediffuses across plasmamembrane into cell.2. Hormone binds toreceptor, inducingconformational change.3. Hormone-receptorcomplex binds to DNA,inducing change ingene activity.

Signal Transduction PathwaysProtein Phosphorylation and DephosphorylationProtein kinase transfers phosphate groups from ATP to a protein (usually another proteing kinase), wich activates the protein, causing the next step in the pathway until the correct protein is activatedThis is turned off by special enzymes which later remove the phosphates from the protein, called protein phosphatasesSecond MessengersSmall molecules or ions that are not proteins and can be triggered inside the cell once reception occursEx: cAMP (in the liver cells for the breakup of glycogen), Ca 2+ (muscle cell contrations, secretion, cell division)

Figure 8-19HOW DO ENZYME-LINKED RECEPTORS WORK?GDPATP1. Signal arrives and binds toreceptor.2. Signal-receptor complex changes conformation and isphosphorylated.5. Phosphorylation cascaderesults, each proteinphosphorylating another untila response is triggered in thecell.SignalRas proteinReceptortyrosinekinase (RTK)GDPADPPADPPRas proteinBridging proteinsGTPPGTPActive protein 1ADPATPATPPPActive protein 2Inactive protein 1Inactive protein 2ADPATPInactive protein 3Triggers response4. Ras catalyzes thephosphorylation of anintracellular protein, activating it.3. Proteins form a bridge to Ras.Ras exchanges its GDP for a GTP.

Cellular ResponsesResponses are triggered either in the nucleus (triggering transcription) or cytoplasm (regulating the proteins activities)Fine-tuning the responseAmplification-cascades where each step produces a greater concentration of activated productsSpecificity of proteins-ex: epi has one effect on the heart and another on the liver because each cell type has different proteins that respond to epi

Todays Plan: 8/13/09Finish AP Lab 3 (1st of class)Finish notes (Last of class)

The Cell CycleInterphase G1 Phase-cell growth (2n l-shaped)S Phase-copying chromosomes in prep. For Mitosis (2n x-shaped)G2 Phase-More cell growth and prep for mitosisMitosis (M Phase)Prophase-mitotic spindles form (centrioles in animal cells only) and attach to spindle at kinetochore (centromere and corresponding DNA Segment)Metaphase-chromosomes migrate to middle of cell (metaphase plate)Anaphase-kinetochore microtubules shorten, pulling chromosomesTelophase-accompanies cytokinesis (2 daughter nuclei, each is 2n l-shaped)Cytokinesis-clevage furrow forms as actin and myosin contract in a ring around the elongated cell in animal cells. In plants, a cell plate forms between the daughter cells, dividing them (results in 2 cells

Figure 11-3Unreplicated chromosomeGene 1Gene 2The DNA replicates,resulting in two copies ofthe same chromosome..Gene 1Gene 2 ReplicatedchromosomeCopies of samechromosomeGene 1Gene 2 CondensedreplicatedchromosomeThe DNA condensesaround its associatedproteins, resulting in acompact chromosomethat is 10,000 times shorterthan its original length.Copies of samechromosome, condensedCentromereThe unreplicated chromosome consists ofa single, long strand of DNA wrappedaround proteins (proteins not shown).

Figure 11-5MitosisMSINTERPHASEDIVISIONG2G1

Figure 11-7a-1PRIOR TO MITOSISChromosomes replicate.CentrosomesChromosomesCentrioles1. Interphase: After chromosomereplication, each chromosome iscomposed of two sister chromatids.Centrosomes have replicated.

Figure 11-7a-2MITOSISSister chromatids separate; one chromosome copy goes to each daughter nucleus.Early mitotic spindleKinetochoreSpindlefibers2. Prophase: Chromosomescondense, and mitotic spindlebegins to form.3. Prometaphase: Nuclearenvelope breaks down.Spindle fibers contactchromosomes at kinetochore.4. Metaphase:Chromosomes completemigration to middle of cell.

Figure 11-7bCYTOKINESISCytoplasmis divided.6. Telophase: The nuclearenvelope re-forms, and thespindle apparatus disintegrates.8. Cell division iscomplete: Twodaughter cells form.7. Cell division begins: Actin-myosin ring causes the plasmamembrane to begin pinching in.5. Anaphase: Sister chromatidsseparate. Chromosomes arepulled to opposite poles of the cell.

Figure 11-7b-16. Telophase: The nuclearenvelope re-forms, and thespindle apparatus disintegrates.5. Anaphase: Sister chromatidsseparate. Chromosomes arepulled to opposite poles of the cell.

Binary FissionBacterial Cell DivisionIn stead of centrioles, chromosome is attached to and remains attached to the plasma membraneThe bacterial cell elongates, separating the chromosome and its copyWhen the growth and separation are complete, cytokinesis occurs

Figure 11-8STEPS IN BACTERIAL CELL DIVISION3. Chromosomespull apart; ringof FtsZ proteinforms.2. Chromosomereplicates.1. Chromosomeis located mid-cell.5. Fissioncomplete.4. FtsZ ringconstricts.Membraneand cell wallinfold.

Controlling the cell cycleCell cycle Control SystemMolecule cycling system for regulationCheckpoints-points in the cycle where the cell is halted until the go ahead chemical signal is given (ex: G1 in animal cells is most critical)Cell Cycle clock-Cyclin-dependent kinases (Cdks) are protein kinases that need cyclin to be active (regulating the levels of cyclin and Cdks regulates the cell cycle)Ex: MPF (maturation promoting factor)-cyclins accumulate during the G2, making Cdks activate which initiate Mitosis. This is turned off during the M phase when proteolytic enzymes break down the cyclin, allowing the cell to proceed through anaphase

Figure 11-14Cyclin concentration regulates MPF concentration.Activated MPF has an array of effects.TimeG1G2G1G2G1SM phaseSM phaseSPPPMPF CdkMPF CyclinMPF activated bydephosphorylationof MPF CdkActivated MPFMPF activated bydephosphorylationof MPF CdkMPF component concentrationPhosphorylate chromosomalproteins; initiate M phasePhosphorylate an enzymethat degrades cyclin; cyclinconcentrations declinePhosphorylate nuclearlamins; initiate nuclearenvelope breakdownPhosphorylate microtubule-associated proteins. Activatemitotic spindle?PCdkCyclinCyclin + Cdk withdephosphorylated,cyclin-dependentkinase subunit

Internal and External Regulating CuesInternal CuesEx: M-phase checkpoint which occurs at Metaphase and ensures that all chromosomes are attached to spindlesKinetochores that arent attached to spindles send signals halting anaphase until theyre attachedExternal CuesGrowth factors released from other body cellsDensity-dependent inhibition-in Biology, we called this contact inhibition (when cells are lost, the Growth factor level increases so cells grow and divide)

Figure 11-181. Growth factorsarrive from othercells.2. Growth factorscause increase incyclin and E2Fconcentration.3. Cyclin binds toCdk; Cdk isphosphorylated.Rb inactivates E2Fby binding to it.4. Cdk is activatedby dephosphorylation.It catalyzesphosphorylation of Rb.5. Rb releases E2F.6. E2F entersnucleus andtriggers productionof S-phase proteins.E2FE2FRbRbE2FE2FE2FADPATPPPPPPRbE2FG1 checkpointpassedS-phaseCdkCdkCyclinCyclinCyclinCyclinCyclinTHE G1 CHECKPOINT IS SUBJECT TO SOCIAL CONTROL

CancerCells that are cancerous dont respond to the cells normal controls of the cell cycleSome cancerous cells divide continuously and spread easily, while others stop completely at one of the various checkpointsCancers can transform adjacent cells to form tumorsBenign=cells remain unchanged within the tumorMalignant=tumor becomes invasive and impairs the organs functionIf cells break away from the tumor and spread through the blood stream, we say they metastasize

Figure 11-17Benign tumorMalignant tumorNormal cellsBenign tumor cellsmay continue todivide, but are notinvasive (they do notspread from tumor)Malignant tumor cellsdivide and spread toadjacent tissues and todistant tissues throughlymphatic vessels andblood vesselsLymph vesselBlood vesselNew tumor that hasformed in distanttissue by metastasis

MeiosisForms the precursors of gametes (Cell goes from 2nn (x-shaped, 2 cells)n (l-shaped, 4 cells)Occurs in 2 divisions: Meiosis I (homologs line up during prophase I and crossing over occurs) and Meiosis II (looks the most like mitosis)

Figure 12-4lPRIOR TO MEIOSISMEIOSIS IChromosomes replicate,forming sister chromatids.NuclearenvelopeChromatin1. Interphase:2. Early Prophase I:Non-sisterchromatidsTetrad (4 chromatids from homologous chromosomes)Spindle apparatusChiasma3. Late Prophase I:4. Metaphase I:Homologous chromosomes separate.5. Anaphase I:Chromosomes replicate in parent cell, in uncondensed state.6. Telophase I and Cytokinesis:Chromosomes condense, nuclear envelope breaks up, spindle apparatus forms. Synapsis of homologous chromosomes.Crossing over of non-sister chromatids (often multiple cross- overs between the same chromatids).Tetrads migrate tometaphase plate.Homologs separate and begin moving to opposite sides of cell.Chromosomes move to opposite sides of cell, then cell divides.

Figure 12-4r7. Prophase II:8. Metaphase II:9. Anaphase II:10. Telophase II andCytokinesis:MEIOSIS IISister chromatids separate.Spindle apparatus forms.Chromosomes line up at middle of cell(metaphase plate).Sister chromatids separate, begin moving to opposite sides of cell.Chromosomes move to opposite sides of cell,then cell divides.

Genetic VariationCrossing overSynapsis of homologs during prophase I causes tetrads with chiasmata (crossing-over of chromatids from neighboring chromosomes), which mixes up sections of the chromosome between homologsUsed to make linkage-mapsIndependent assortmentInheritance of one chromosome doesnt affect the inheritance of another (non-linkage)Random fertilizationYou never know which resultant sperm will fertilize which resultant egg

Figure 12-7-2A CLOSER LOOK AT THREE KEY EVENTS IN MEIOSISCentromereNon-sisterchromatidsProtein complex3. Crossing over,Crossing over usually occurs at least once in each non-sister chromatid, but is only shown on 1 pair here during prophase I. Complex of proteins forms where crossing over will occur. Chromosome segments are swapped between non-sister chromatids.

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