AP Biology Day 50 - Weeblyflemingapbio.weebly.com/.../ap_bio_day_50_2017_ch_15_complete.pdf · AP Biology Day 50 Friday, January 20, 2017. Do-Now 1. ... CH. 15 VCN (Linked Genes)

AP Biology Day 50 Friday, January 20, 2017

Do-Now

1.   ReviewyourGene/csProblemswithyourneighbors

2.   PrepareforyourCh.14quiz

Announcements• Makesuretohaveacalculator• Completeprac/cequizzes!•  Semester2Grades

– Receivea3+onAPexamfor+10%toyourfinalsemester2grade

– Onlyappliestostudentswhocompletedallwork

CW/HWAssignments6.  CH.15VCN(LinkedGenes)7.  Ch.15LectureNotes8.  GeneDcsWS3

PLANNER •  Complete odd #s for Genetics WS 3 (separate paper) •  See Ms. Fleming for ALL stamps •  Ch. 15 Quiz •  Study for genetics test

– Ch. 13-15, with some Ch. 6-7

QuizProtocol

• Clearyourdesks• Noiselevel0• Eyesonyourownpaper• Checkanswerswhenfinished• Flipoverwhenfinished

EssenDalknowledgestandards•  3.A.4:TheinheritancepaSernofmanytraitscannotbeexplainedbysimpleMendeliangene/cs

•  3.C.1:Changesingenotypecanresultinchangesinphenotype

FLT•  Iwillbeableto:– Explainwhysex-linkeddiseasesaremore

commoninhumanmalesthanfemales

– disDnguishbetweensex-linkedgenesandlinkedgenes

– Explainhowmeiosisaccountsfor

recombinantphenotypes

– Explainhowlinkagemapsareconstructed

•  Bycomple1ngCh.15LectureNotes

Ch.15:TheChromosomalBasisofInheritance

Overview•  Mendel’s�hereditaryfactors�weregenes,thoughthiswasn’tknownattheDme.

•  ThelocaDonofaparDculargenecanbeseenbytaggingisolatedchromosomeswithafluorescent

dyethathighlightsthegene.

9

I.MendelianGeneDcsandChromosomesA.  ChromosomeTheoryofInheritance

•  Thechromosometheoryofinheritancestates:

– Mendeliangeneshavespecificloci(posi/ons)onchromosomes

– Chromosomesundergosegrega/onandindependentassortment.

•  ThebehaviorofchromosomesduringmeiosiswassaidtoaccountforMendel�slawsofsegregaDonandindependentassortment.

10

Mendel�sLawsPGenera/on Yellow-round

seeds(YYRR)

Y

F1Genera/on

Y

R R

R Y

× rr

r

y

y

y

Meiosis

Fer/liza/on

Gametes

Green-wrinkledseeds( yyrr)

AllF1plantsproduceyellow-roundseeds(YyRr)

R R

YYr r

y y

Meiosis

R R

Y Y

r r

y y

MetaphaseI

Y Y

R Rrr

y yAnaphaseI

r r

y Y

MetaphaseIIR

Y

R

y

yyy

RR

YY

rrrr

yYYR R

yRYryrYR1/4 1/4 1/4 1/4

F2Genera/on

Gametes

AnF1×F1cross-fer/liza/on

9 :3 :3 :1

LAWOFINDEPENDENTASSORTMENTAllelesofgenesonnonhomologouschromosomesassortindependentlyduringgameteforma/on.

LAWOFSEGREGATIONThetwoallelesforeachgeneseparateduringgameteforma/on.

1

2

33

2

1

I.MendelianGeneDcsandChromosomes

WhatwereMendel’shereditaryfactors?

Whereweretheylocated??

12

I.MendelianGeneDcsandChromosomesA.  MorganandDrosophilaMelanogaster

•  ThomasHuntMorganstudiedmutaDonin

Drosophlamelanogaster(fruitflies)•  Morgan�sexperimentswithfruitfliesprovidedconvincingevidencethatchromosomesarethe

locaDonofMendel’sheritablefactors

13

I.MendelianGeneDcsandChromosomesA.  ChromosomeTheoryofInheritance

B.  MorganandDrosophilaMelanogaster

•  SeveralcharacterisDcsmakefruitfliesaconvenient

organismforgeneDcstudies:

– Theybreedatahighrate– AgeneraDoncanbebredeverytwoweeks– Theyhaveonlyfourpairsofchromosomes.

14

I.MendelianGeneDcsandChromosomes

A.  MorganandDrosophila

Melanogaster

1.  Wildtypeandmutant

type

–  Differenttraitshavebeen

studied

–  Commonly,eyecoloris

lookedat

–  Ex/

–  Wildtype=red-eyes–  Mutanttype=whiteeyes

15

Normal/WildTypeMutant/AlternaDve

Phenotypes


•  Inoneexperiment,Morganmatedmaleflieswithwhiteeyes(mutant)withfemaleflieswithredeyes(wildtype)

– TheF1generaDonallhadredeyes– TheF2generaDonshowedthe3:1red:whiteeyeraDo,butonlymaleshadwhiteeyes.

•  Morgandeterminedthatthewhite-eyedmutantallelemustbelocatedontheXchromosome.

•  Morgan’sfindingsupportedthechromosometheoryofinheritance.

17

Recall:SexChromosomesvs.Autosomes

18

II.InheritanceofSex-LinkedGenes•  Thesexchromosomeshavegenesformany

charactersunrelatedtosex.

•  Sex-linkedgene=Agenelocatedononeofthesexchromosomes

•  Inhumans,sex-linkedusuallyreferstoageneon

thelargerXchromosome.

19

Recall:SexChromosomesvs.Autosomes

20


•  P:Morgancrossedared-eyedfemalewithawhite-

eyedmale

•  F1:Allred-eyedoffspring•  F2:3red-eyed:1white-eyedmale

•  Haveweseenthispadernbefore?

21

I.MendelianGeneDcsandChromosomesNotaDonforX-linkedtraits:

•  XA=dominantallele,Xa=recessiveallele

•  MalesalwaysexhibitX-linkedtraitstheyinherit(dominantornot)sincetheyonlyhaveoneX

•  Examples:

– XRXR=homozygousdominantred-eyedfemale

– XRXr=heterozygousred-eyedfemale

– XrXr=homozygousrecessivewhite-eyedfemale

– XRY=red-eyedmale

– XrY=white-eyedmale

22

I.MendelianGeneDcsandChromosomesExample:PgeneraDon

True-breedingred-eyedfemalexwhite-eyedmale

23

I.MendelianGeneDcsandChromosomesDo-Now:

CrosstheF1(heterozygousfemalexred-eyedmale)

24

II.InheritanceofSex-LinkedGenesA.  SexDeterminaDon

•  Inhumansandothermammals,therearetwo

varieDesofsexchromosomes:alargerX

chromosomeandasmallerYchromosome.

•  OnlytheendsoftheYchromosomehaveregions

thatarehomologouswiththeXchromosome.

•  TheSRYgeneontheYchromosomecodesforthedevelopmentoftestes.

25

SystemsofSexDetermina/on

44+XY Parents 44+

XX

22+X

22+X

22+Yor +

44+XX or

Sperm Egg

44+XY

Zygotes(offspring)

(a)TheX-Ysystem

22+XX

22+X

(b)TheX-0system

76+ZW

76+ZZ

(c)TheZ-Wsystem

32(Diploid)

16(Haploid)

(d)Thehaplo-diploidsystem

II.InheritanceofSex-LinkedGenesB.Sex-Linkedinheritedtraits

•  Sex-linkedgenesfollowspecificpadernsofinheritance.

•  Forarecessivesex-linkedtraittobeexpressed– Afemaleneedstwocopiesoftheallele

– Amaleneedsonlyonecopyoftheallele

•  BecausemalesalwaysexpressX-linkedgenes,sex-linkedrecessivedisordersaremuchmorecommoninmalesthaninfemales.

27

(a) (b) (c)

XNXN XnY XNXn× × XNY XNXn × XnY

YXnSpermYXNSpermYXnSperm

XNXnEggs XN

XN XNXn

XNY

XNY

Eggs XN

Xn

XNXN

XnXN

XNY

XnY

Eggs XN

Xn

XNXn

XnXn

XNY

XnY

N=Normalisdominant

n=disorderisrecessive

II.InheritanceofSex-LinkedGenesC.Hemizygous

=Havingonlyonecopyofagene(insteadoftwo)Ex/MalesaretypicallyhemizygousforX-chromosome

genes

29

II.InheritanceofSex-LinkedGenesD.SomedisorderscausedbyrecessiveallelesontheX

chromosomeinhumans:

1.Musculardystrophy

2.Colorblindness

3.Hemophilia

30

II.InheritanceofSex-LinkedGenesE.X-InacDvaDoninFemales

1.Barrbodies

•  Inmammalianfemales,oneofthetwoXchromosomesineachcellisrandomlyinac/vatedduringembryonicdevelopment.

•  Theinac/veXcondensesintoaBarrbody.•  IfafemaleisheterozygousforaparDculargene

locatedontheXchromosome,shewillbeamosaic

forthatcharacter.

31

XInac/va/onisRandominFemaleMammalCells

Xchromosomes

Earlyembryo:

Allelefororangefur

Alleleforblackfur

CelldivisionandXchromosomeinac/va/onTwocell

popula/onsinadultcat:

Ac/veXAc/veX

Inac/veX

Blackfur Orangefur

33

III.ChromosomalRecombinaDonA.  LinkedGenes

34

III.ChromosomalRecombinaDonA.  LinkedGenes

35

III.ChromosomalRecombinaDonA.  LinkedGenes•  Linkedgenes=genesonthesamechromosomethattendtobeinheritedtogetherduetoproximity

•  Morgandidotherexperimentswithfruitfliestosee

howlinkageaffectsinheritanceoftwocharacters.

•  Morgancrossedfliesthatdifferedintraitsofbody

colorandwingsize.

36

Morgan:LinkedGenes

b+ vg+

Parentsintestcross

Mostoffspring

b+ vg+

b vg

b vg

b vg

b vg

b vg

b vg

×

or

EXPERIMENT

Morgan: Linked Genes P Generation (homozygous)

RESULTS

Wild type (gray body, normal wings)

Double mutant (black body, vestigial wings) ×

b b vg vg

b b vg vg

Double mutant TESTCROSS

×

b+ b+ vg+ vg+

F1 dihybrid (wild type)

b+ b vg+ vg

Testcross offspring Eggs b+ vg+ b vg b+ vg b vg+

Black- normal

Gray- vestigial

Black- vestigial

Wild type (gray-normal)

b vg

Sperm

b+ b vg+ vg b b vg vg b+ b vg vg b b vg+ vg PREDICTED RATIOS

If genes are located on different chromosomes:

If genes are located on the same chromosome and parental alleles are always inherited together:

1

1

1

1

1 1

0 0

965 944 206 185

:

:

:

:

:

:

:

:

:

III.ChromosomalRecombinaDonB.GeneDcRecombinaDon

•  Evenwhengenesarelinked,geneDcrecombinaDon

canoccur

– Thismeansthatnewphenotypes(non-parentalphenotypes)areproduced

•  Gene/crecombina/on=Parentsproduceoffspringwithamixoftraits(notiden/caltoparents)

•  ThegeneDcfindingsofMendelandMorganrelate

tothechromosomalbasisofrecombina/on.

39

III.ChromosomalRecombinaDonC.ParentalTypes

•  Parentaltypes=phenotypesthatmatchoneoftheparents

40

III.ChromosomalRecombinaDonD.Recombinants

•  Non-parentalphenotypes=recombinants

41

ParentalTypesandRecombinants

YyRr

Gametesfromgreen-wrinkledhomozygousrecessiveparent(yyrr)

Gametesfromyellow-roundheterozygousparent(YyRr)

Parental-type

offspring

Recombinantoffspring

yr

yyrr Yyrr yyRr

YR yr Yr yR

Crossing Over: Separates Linked Genes Recombinant Frequency Calculated

Testcross parents

Replication of chromosomes

Gray body, normal wings (F1 dihybrid)

Black body, vestigial wings (double mutant)

Replication of chromosomes

b+ vg+

b+ vg+

b+ vg+

b vg

b vg

b vg

b vg

b vg

b vg

b vg b vg

b vg

b+ vg+

b+ vgb vg+

b vg

Recombinant chromosomes

Meiosis I and II

Meiosis I

Meiosis II

b vg+b+ vgb vg b+ vg+ Eggs

Testcross offspring

965 Wild type

(gray-normal)

944 Black-

vestigial

206 Gray-

vestigial

185 Black- normal

b+ vg+

b vg b vg

b vg b+ vg

b vg b vg

b vg+

Sperm

b vg

Parental-type offspring Recombinant offspring

Recombination frequency = 391 recombinants

2,300 total offspring × 100 = 17%

III.ChromosomalRecombinaDonE.CrossingOver–

1.RecombinaDonFrequency=%ofrecombinant

offspringproducedinageneDccross

•  Genesondifferentchromosomesà50%recombina/onfrequency

•  Ifgenesarelinked,thentheymaynotassortindependentlyduringmeiosis.Thus,LESSTHAN50%recombina/onfrequency

44

45

IV.GeneDcMaps&CrossingOverData•  AlfredSturtevant,oneofMorgan�sstudents,constructedagene/cmap,anorderedlistofthegeneDclocialongaparDcularchromosome

•  Sturtevantpredictedthatthefartheraparttwogenesare,thehighertheprobabilitythatacrossoverwilloccurbetweenthemandthereforethehighertherecombina9onfrequency.

46

IV.GeneDcMaps&CrossingOverDataA.  Linkagemap/Mapunits

•  Linkagemap=mappinggenesonachromosomebasedonrecombina/onfrequencies

•  Distancesbetweengenescanbeexpressedasmap

units;onemapunit,orcenDmorgan,representsa

1%recombinaDonfrequency.

•  Mapunitsindicaterela/vedistanceandorder,notpreciseloca/onsofgenes.

47

CrossingOver-->RecombinantsFrequency-->DistanceApart

RESULTS

Recombina/onfrequencies

Chromosome9% 9.5%

17%

b cn vg

IV.GeneDcMaps&CrossingOverDataA.  Linkagemap/Mapunits

•  Genesthatarefarapartonthesamechromosomecan

havearecombinaDonfrequencynear50%.

•  Suchgenesarephysicallylinked,butgeneDcallyunlinked,andbehaveasiffoundondifferentchromosomes.

•  SturtevantusedrecombinaDonfrequenciestomake

linkagemapsoffruitflygenes.

•  Usingmethodslikechromosomalbanding,geneDcistscan

developcytogeneDcmapsofchromosomes.

•  CytogeneDcmapsindicatetheposiDonsofgeneswith

respecttochromosomalfeatures.

49

Pair-Share-Respond1.  Whatismeantbytheterm“linkedgenes”?2.  What%recombina/onfrequencywouldbe

expectedforlinkedgenes?3.  What%recombina/onfrequencywouldbe

expectedforgenesthatarenotlinked?4.  Whatisalinkagemap,andwhatdoesittell

us?

50

V.ChromosomalAlteraDons•  WhatkindofchromosomalalteraDonscanoccur

andwhataretheireffects?

51

V.ChromosomalAlteraDonsA.  AlteraDonsinChromosomeNumber

1.Nondisjunc/on=whenhomologouschromosomesdonotseparateduringanaphaseIofmeiosis• Thiscausesonegametetoreceive2copiesofachromosome,andanothergametetohavenocopies

2.Aneuploidy–

3.Polyploidy-

52

Fig.15-13-3

MeiosisI

Nondisjunc/on

(a) Nondisjunction of homologous chromosomes in meiosis I

(b) Nondisjunction of sister chromatids in meiosis II

MeiosisII

Nondisjunc/on

Gametes

Numberofchromosomes

n+1 n+1 n+1n–1 n–1 n–1 n n


2.Aneuploidy=whenthegametesresul/ngfromnondisjunc/onarefer/lized,anabnormalchromosomenumberresults

•  AmonosomiczygotehasonlyonecopyofaparDcularchromosome2n-1

•  AtrisomiczygotehasthreecopiesofaparDcularchromosome2n+1

3.Polyploidy-

54


3.Polyploidy–

•  Polyploidy=whenanorganismhasmorethantwocompletesetsofchromosomes– Triploidy(3n)isthreesetsofchromosomes

– Tetraploidy(4n)isfoursetsofchromosomes

•  Polyploidyiscommoninplants,butnotanimals

•  Polyploidsaremorenormalinappearancethan

aneuploids.

55

V.ChromosomalAlteraDonsB.AlteraDonsofChromosomeStructure

•  Breakageofachromosomecanleadtofourtypesof

changesinchromosomestructure:

1.   Dele/on=removesachromosomalsegment2.   Duplica/on=repeatsasegment3.   Inversion=reversesasegmentwithinachromosome4.   Transloca/on=movesasegmentfromone

chromosometoanother.5.   NonreciprocalCrossover=resultsinonechromosome

havingadele/onandanotheraduplica/on

56

BreakageCausesChange

Dele/onABCDEFGH ABCEFGH(a)

(b)

(c)

(d)

Duplica/on

Inversion

Reciprocaltransloca/on

ABCDEFGH

ABCDEFGH

ABCDEFGH

ABCBCDEFGH

ADCBEFGH

MNOCDEFGH

MNOPQR ABPQR

V.ChromosomalAlteraDonsC.ChromosomalAlteraDonsinHumanDisease

1.AneuploidDisorders=causedbynondisjunc/onofsexchromosomes

58

V.ChromosomalAlteraDons1.AneuploidDisorders

a.DownSyndrome=resultsfromthreecopiesofchromosome21

•  Itaffectsaboutoneoutofevery700childrenbornintheUnitedStates.

•  ThefrequencyofDownsyndromeincreaseswith

theageofthemother,acorrelaDonthathasnot

beenexplained.

59

Down Syndrome 2n + 1 trisomy 21


b.KlinefelterSyndrome=resultsfromanextrachromosomeinmales(XXY)

•  EffectsincludelowIQ,tallerbody,decreasedmusclemass,broadhips,extendedlegs,weaker

bones,etc.

61


c.Turnersyndrome=MonosomyX=XOfemales

– Viable,butfemalesaresterile

62


d.ExtraY=XYYmales(occursin1/1000malebirths)•  Taller,possibleacneissues,butmostlynormal

63


e.Metafemales=XXX(about1:1500femalebirths)•  Taller,poorcoordinaDon,reproducDveconcerns

64

V.ChromosomalAlteraDonsC.ChromosomalAlteraDonsinHumanDisease

2.StructuralDiseases

a.Criduchat=“cryofthecat”=dele/onofchromosome5

•  Resultsinseveredevelopmentaldelays,behavioral

struggles,unusualfacialfeatures,andnervous

systemissues.

65

VI.ExcepDonstoStandardChromosomeTheory

OneexcepDontochromosometheoryinvolvesgenes

locatedinthenucleus

A.   GenomicImprin/ng=varia/oninphenotypethatdependsonwhichparentpassedthealleles(mothervs.father)

•  GenomicimprinDnginvolvesthesilencingofcertain

genesthatare�stamped�withanimprintduring

gameteproducDon.

66

Genomic Imprinting

Normal Igf2 allele is expressed

Paternal chromosome

Maternal chromosome

Normal Igf2 allele is not expressed

Mutant Igf2 allele inherited from mother

(a) Homozygote

Wild-type mouse (normal size)

Mutant Igf2 allele inherited from father

Normal size mouse (wild type)

Dwarf mouse (mutant)

Normal Igf2 allele is expressed

Mutant Igf2 allele is expressed

Mutant Igf2 allele is not expressed

Normal Igf2 allele is not expressed

(b) Heterozygotes


A.  GenomicImprinDng:

•  ItappearsthatmammaliangenomicimprinDng,

�genesilencing,�istheresultofthemethyla9onofDNA(addiDonof–CH3).

•  GenomicimprinDngisthoughttoaffectonlyasmall

fracDonofmammaliangenes.

•  MostimprintedgenesarecriDcalforembryonic

development.

68


B.   OrganelleGenes=extranuclearDNA(suchasthatfoundinmitochondriaandchloroplasts)areinheritedmaternallybecausethezygote’scytoplasmcomesfromtheegg

•  Thefirstevidenceofextranucleargenescamefromstudiesontheinheritanceofyelloworwhitepatchesonleavesofanotherwisegreenplant.

69

REVIEW EggSperm

Pgenera/ongametes

CBAD E

F

D

F EA

BCe

d

fcba

d

f

e

cba

ThisF1cellhas2n=6chromosomesandisheterozygousforallsixgenesshown(AaBbCcDdEeFf ).Red=maternal;blue=paternal.

+

Eachchromosomehashundredsorthousandsofgenes.Four(A, B, C, F)areshownonthisone.

Theallelesofunlinkedgenesareeitheronseparatechromosomes(suchasdande)orsofarapartonthesamechromosome(candf )thattheyassortindependently.

Genesonthesamechromo-somewhoseallelesaresoclosetogetherthattheydonotassortindependently(suchasa, b,andc)aresaidtobelinked.

RecombinantsDuetoCrossing-Over

Assignment1.  GeneDcsset#3(odd)

72

AP Biology Day 50 - Weeblyflemingapbio.weebly.com/.../ap_bio_day_50_2017_ch_15_complete.pdf · AP Biology Day 50 Friday, January 20, 2017. Do-Now 1. ... CH. 15 VCN (Linked Genes)

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