AP Biology Day 47 Wednesday, January 11, 2017

Do-Now1.   TurninbreakHWtoboxàmust

becomplete(everyques8ona9empted).

2.   TurninUnitLogstobox3.   Labsturnedinbyneatlystacking

themonthebacktable4.   Haveoutyourunitlogs,

planners,andCh.13NotesOutline

CW/HWAssignments1.  Ch.13LectureNotes2.  Ch.13VideoCornellNotes(2)3.  Ch.14GuidedReading

PLANNER •  Complete Ch. 13 VCN (2) tonight •  Complete Ch. 14 GR by Friday •  Ch. 13 Quiz

EssenFalknowledgestandards•  3.A.2:Ineukaryotes,heritableinforma8onispassedtothenextgenera8onviaprocessesthatincludethecellcycleandmitosisormeiosisplusfer8liza8on.

•  3.C.2:Biologicalsystemshavemul8pleprocessesthatincreasegene8cvaria8on.

FLT•  Iwillbeableto:– describetheeventsthatcharacterizeeachphaseofmeiosis

– disFnguishbetweenthefollowingterms:somaFccellandgamete;autosomeandsexchromosomes;haploidanddiploid

– NameandexplainthethreeeventsthatcontributetogeneFcvariaFoninsexuallyreproducingorganisms

•  Bycomple1ngCh.13LectureNotes

Ch.13:Meiosis&SexualLifeCycles

Recap

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DNAvs.Chromosomes

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Mitosis

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FerFlizaFon

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SomaFcCellsvs.Gametes

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HomologousChromosomes

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Autosomesvs.SexChromosomes

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III.SexualLifeCycles

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MeiosisOverview

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•  Meiosis•  Occursinthegonads(ovariesandtestes)•  Reducesthechromosomenumberbyhalf(2nàn)•  Produceshaploidgametes

•  Fer8liza8on(n+n)restoresthenormalchromosomenumber.

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HumanLifeCycle

KeyHaploid(n)Diploid(2n)

Haploidgametes(n=23)

Egg(n)

Sperm(n)

MEIOSIS FERTILIZATION

Ovary Tes8s

Diploidzygote(2n=46)

Mitosisanddevelopment

Mul8cellulardiploidadults(2n=46)

Pair-Share-Respond1.   Dis8nguishbetweentheterms“haploid”+

“diploid”.2.   Whatkindofcellswouldbehaploidandwhat

kinddiploid?3.   Explainhowmeiosisandfer8liza8onwork

togethertomaintainaconstantnumberofchromosomes

4.   Dis8nguishbetweenspermatogenesisandoogenesis.

IV.Meiosis•  Likemitosis,meiosisisprecededbythereplicaFonofchromosomes.

•  Meiosistakesplaceintwosetsofcelldivisions,calledmeiosisIandmeiosisII.

•  Reduc8onDivision2n-->n.•  Meiosishastwocelldivisionsandresultsinfourdaughtercells.

•  Eachdaughtercellhasonlyhalfasmanychromosomesastheparentcell.

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IV.Meiosis•  1stDivision=meiosisI•  Homologouschromosomesseparate

•  Twodaughtercellsareproduced•  ReducFondivision

•  2ndDivision=meiosisII•  Resultsinfourhaploiddaughtercells•  EquaFonalDivision

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Fig.13-7-3

Meio8cCellDivision:Reduc8onDivision2n-->n

Interphase

Homologouspairofchromosomesindiploidparentcell

Chromosomesreplicate

Homologouspairofreplicatedchromosomes

Sisterchroma8ds Diploidcellwith

replicatedchromosomes

MeiosisI

Homologouschromosomesseparate

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Haploidcellswithreplicatedchromosomes

MeiosisII

2 Sisterchroma8dsseparate

Haploidcellswithunreplicatedchromosomes

IV.Meiosis•  Interphase=chromosomesarereplicatedtoformsisterchromaFds=occursbeforemeiosisI

•  ThesisterchromaFdsaregeneFcallyidenFcalandjoinedatthecentromere.

•  Thesinglecentrosomereplicates,formingtwocentrosomes.

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IV.MeiosisA.  StagesofMeiosisI•  DivisioninmeiosisIoccursinfourphases:

–ProphaseI:synapsis/crossing-over

–MetaphaseI:randomalignmentatequator

–AnaphaseI:independentassortment–homologouschromosomesseparate

–TelophaseIandcytokinesis

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Metaphase I

Fig. 13-8a

Prophase I Anaphase I Telophase I and Cytokinesis

Centrosome (with centriole pair)

Sister chromatids Chiasmata

Spindle

Homologous chromosomes

Fragments of nuclear envelope

Centromere (with kinetochore)

Metaphase plate

Microtubule attached to kinetochore

Sister chromatids remain attached

Homologous chromosomes separate

Cleavage furrow

Meiosis I:

Variety Increases

ProphaseI:Synapsis+CrossingOver•  Synapsis=homologouschromosomeslooselyaligngenebygene.

•  Tetrad=paireduphomologs

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IV.MeiosisProphaseI:Synapsis+CrossingOver•  Crossingover=nonsisterchroma8dsexchangeDNAsegments,whichcancreategene0cvaria0on.

•  Eachtetradusuallyhasoneormorechiasmata,X-shapedregionswherecrossingoveroccurred.

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IV.MeiosisMetaphaseI:RandomAlignmentatMiddle

•  InmetaphaseI,tetradslineuprandomlyatthemetaphaseplate(middle),withonechromosomefacingeachpole.

•  Microtubulesfromonepoleareadachedtothekinetochoreofonechromosomeofeachtetrad.

•  Microtubulesfromtheotherpoleareadachedtothekinetochoreoftheotherchromosome.

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IV.MeiosisAnaphaseI:Separa8onofHomologousPairs•  InanaphaseI,pairsofhomologouschromosomesseparate.

•  Onechromosomemovestowardeachpole,guidedbythespindleapparatus:depolymerizaFonofthespindlefibers/microtubules.

•  SisterchromaFdsremainadachedatthecentromereandmoveasoneunittowardthepole.

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IV.MeiosisTelophaseIandCytokinesis:•  InthebeginningoftelophaseI,eachhalfofthecellhasahaploidsetofchromosomes;eachchromosomesFllconsistsoftwosisterchromaFds

•  Cytokinesisusuallyoccurssimultaneously,formingtwohaploiddaughtercells.

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IV.Meiosis•  Animalcellsàcleavagefurrow(acFn)forms•  Plantcellsàcellplate(Golgivesicles-membrane)forms.

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MeiosisI

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IV.Meiosis•  NochromosomereplicaFonoccursbetweentheendofmeiosisIandthebeginningofmeiosisIIbecausethechromosomesarealreadyreplicated.

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IV.MeiosisB.  StagesofMeiosisII–verysimilartomitosis

1.  ProphaseII–nuclearenvelopebreaksdown2.  MetaphaseII–chromosomeslineupatplate

3.  AnaphaseII–sisterchromaFdsseparate

4.  TelophaseII/Cytokinesis–newnucleiformandcytokinesisoccurs

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Fig.13-8d

ProphaseII MetaphaseII AnaphaseII TelophaseIIandCytokinesis

Sisterchroma8dsseparate Haploiddaughtercells

forming

MeiosisII:SisterChroma8dsSeparate-->4HaploidCells

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IV.Meiosis•  Cytokinesisseparatesthecytoplasm.

•  Endofmeiosisà4gene8callyuniquehaploid(n)daughtercells

•  Meiosis:VARIETYincreaseswithreduc8ondivision2n-->n.

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V.ComparingMitosisandMeiosisA.  Mitosis–

–  Asexualreproduc8on–  Produces2gene8callyiden8caldaughtercells–  Chromosome#staysthesame(2nà2n)–  Canoccurinallorganisms

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V.ComparingMitosisandMeiosisB.  Meiosis

–  Increasesgene8cdiversitythroughsexualreproduc8on

–  Produces4gene8callyuniquehaploiddaughtercells–  Reducesthechromosomenumberbyhalf–  Createsgametes

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V.ComparingMitosisandMeiosisC.  SimilariFes–

–  ThemechanismforseparaFngsisterchromaFdsisvirtuallyidenFcalinmeiosisIIandmitosis.

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VI.EventsUniquetoMeiosisA.  AtProphaseI-synapsis+crossingoverB.  AtMetaphaseI–randomassortmentofhomologs

atmetaphaseplate

C.  AtAnaphaseI–separaFonofhomologs

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Pair-Share-Respond1.   Whataretheresultsofmeiosis

(overall)?2.   Describe,specifically,whatoccursin

prophaseIofmeiosis.3.   Whendohomologouschromosomes

separate?4.   Whendosisterchroma8dsseparate?5.   Iden8fythreedifferencesbetween

meiosisandmitosis

VII.OriginsofGeneFcVariaFonAmongOffspring

•  Muta8ons(changesinanorganism�sDNA)aretheoriginalsourceofgeneFcdiversity.

•  MutaFonscreatedifferentversionsofgenescalledalleles.

•  SexualReproduc8on/Recombina8ons-reshufflingofallelesduringsexualreproducFonproducesgeneFcvariaFon

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VII.OriginsofGeneFcVariaFonAmongOffspring•  ThreemechanismsinSexualReproduc0oncontributeto

geneFcvariaFon:

– IndependentassortmentofchromosomesatequatorofMetaphaseI.

– Crossingover-ProphaseI:synapsis/tetrad– Randomfer8liza8onThenumberofcombina8onspossiblewhenchromosomesassortindependentlyintogametesis2n,wherenisthehaploidnumber.

•  Forhumans(n=23),therearemorethan8million(223)possiblecombinaFonsofchromosomes.

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Fig.13-11-3

Possibility1 Possibility2

TwoequallyprobablearrangementsofchromosomesatmetaphaseI

MetaphaseII

Daughtercells

Combina8on1 Combina8on2 Combina8on3 Combina8on4

VII.OriginsofGeneFcVariaFonAmongOffspring•  Crossingoverproducesrecombinantchromosomes,which

combinegenesinheritedfromeachparent.

•  CrossingoverbeginsveryearlyinprophaseI,ashomologouschromosomespairupgenebygene.

•  Incrossingover,homologousporFonsoftwononsisterchromaFdstradeplaces.

•  CrossingovercontributestogeneFcvariaFonbycombiningDNAfromtwoparentsintoasinglechromosome.

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Fig.13-12-5ProphaseIofmeiosis

Pairofhomologs

Nonsisterchroma8dsheldtogetherduringsynapsis

Chiasma

Centromere

AnaphaseI

AnaphaseII

Daughtercells

Recombinantchromosomes

TEM

VII.OriginsofGeneFcVariaFonAmongOffspring•  RandomferFlizaFonaddstogeneFcvariaFonbecauseanyspermcanfusewithanyovum(unferFlizedegg).

•  Thefusionoftwogametes(eachwith8.4millionpossiblechromosomecombinaFonsfromindependentassortment)producesazygotewithanyofabout70trilliondiploidcombinaFons.

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VIII.EvoluFonarySignificanceofGeneFcVariaFonWithinPopulaFons•  NaturalselecFonresultsintheaccumulaFonofgeneFcvariaFonsfavoredbytheenvironment.

•  SexualreproducFoncontributestothegeneFcvariaFoninapopulaFon,whichoriginatesfrommutaFons.

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HW•  FinishCh.13Notes•  Ch.14GuidedReading•  Ch.13VideoCornellNotes(2)

– Ch.13Quiznextclass!

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