文本分析參考

FigureFigureConcept14.1:MendelusedConcept14.1:Mendelusedtheapproachtoidentifytwolawsof?MendeldiscoveredthebasicprinciplesofhereditybybreedinggardenpeasincarefullyplannedexperimentsMendel’sExperimental,QuantitativeMendel’sExperimental,QuantitativeAdvantagesofpeaplantsforgeneticTherearemanyvarietieswithdistinctheritablefeatures,orcharacters(suchasflowercolor);charactervariants(suchaspurpleorwhiteflowers)arecalledtraitsMatingcanbeEachflowerhassperm-producingorgans(stamens)andegg-producingorgan(carpel)Cross-pollination(fertilizationbetweendifferentplants)involvesdustingoneplantwithpollenfromanother?Figure123Figure12345Firstfilial?Mendelchosetotrackonlythosecharactersthatoccurred?MendelchosetotrackonlythosecharactersthatoccurredintwodistinctalternativeformsHealsousedvarietiesthattrue-breeding純育生(plantsthatproduceoffspringofthesamevarietywhentheyself-pollinate)??Inatypicalexperiment?InatypicalexperimentMendelmatedtwocontrasting,true-breedingvarieties,aprocesscalledhybridization雜交orThetrue-breedingparentsarethePgeneration親代ThehybridoffspringofthePgenerationarecalledtheF1generation子代(filial)WhenF1individualsself-pollinateorcross-pollinatewithotherF1hybrids,theF2generationisproduced???TheLawofSegregation分TheLawofSegregation分離定?WhenMendelcrossedcontrasting,true-breedingwhite-andpurple-floweredpeaplants,alloftheF1hybridswerepurpleWhenMendelcrossedtheF1hybrids,manyoftheF2plantshadpurpleflowers,butsomehadwhiteMendeldiscoveredaratioofaboutthreetoone,purpletowhiteflowers,intheF2??Figure14.3-PGenerationFigure14.3-PGenerationFigure14.3-PGenerationFigure14.3-PGenerationAllplantshadpurpleSelf-orcross-Figure14.3-PGenerationFigure14.3-PGenerationAllplantshadpurpleSelf-orcross-F2?Mendelreasonedthatonlythepurpleflowerfactorwasaffectingflower?MendelreasonedthatonlythepurpleflowerfactorwasaffectingflowercolorintheF1hybridsMendelcalledthepurpleflowercolor?andtheflowercolorarecessivetrait隱形特ThefactorforwhiteflowerswasnotdilutedordestroyedbecauseitreappearedintheF2generation?Mendelobservedthesamepatternofinheritanceinsixotherpeaplantcharacters,eachrepresentedbyMendelobservedthesamepatternofinheritanceinsixotherpeaplantcharacters,eachrepresentedbytwotraitsWhatMendelcalleda“heritablefactor”iswhatwenowcallagene???2011PearsonEducation,TableTableMendel’sMendeldevelopedaMendel’sMendeldevelopedahypothesistoexplainthe3:1inheritancepatternheobservedinF2offspringFourrelatedconceptsmakeupthisTheseconceptscanberelatedtowhatwenowknowaboutgenesandchromosomes????2011PearsonEducation,?First:alternativeversionsofgenesaccountforvariationsininherited?First:alternativeversionsofgenesaccountforvariationsininheritedForexample,thegeneforflowercolorinpeaplantsexistsintwoversions,oneforpurpleflowersandtheotherforwhiteThesealternativeversionsofagenearenowcalledalleles等位基因Eachgeneresidesataspecificlocusonaspecificchromosome基因座???FigureAlleleforpurpleFigureAlleleforpurplePairofLocusforflower-colorAlleleforwhite?Second:foreachcharacter,anorganisminheritstwoalleles,one?Second:foreachcharacter,anorganisminheritstwoalleles,onefromeachparentMendelmadethisdeductionwithoutknowingabouttheroleofchromosomesThetwoallelesataparticularlocusmaybeidentical,asinthetrue-breedingplantsofMendel’sPgenerationAlternatively,thetwoallelesatalocusmaydiffer,asintheF1hybrids????Third:ifthe?Third:ifthetwoallelesatalocusdiffer,thenone(thedominantallele)determinestheorganism’sappearance,andtheother(therecessiveallele)hasnonoticeableeffectonappearanceIntheflower-colorexample,theF1plantshadpurpleflowersbecausethealleleforthattraitisdominant??Fourth:(nowknownasthelawofsegregation):thetwo?Fourth:(nowknownasthelawofsegregation):thetwoallelesforaheritablecharacterseparate(segregate)duringgameteformationandendupindifferentThus,aneggoraspermgetsonlyoneofthetwoallelesthatarepresentintheThissegregationofallelescorrespondstothedistributionofhomologouschromosomestodifferentgametesin???Mendel’ssegregationmodelaccounts?Mendel’ssegregationmodelaccountsforthe3:1ratioheobservedintheF2generationofhisnumerouscrossesThepossiblecombinationsofspermandeggcanbeshownusingaPunnettsquare龐氏表,adiagramforpredictingtheresultsofageneticcrossbetweenindividualsofknowngeneticmakeupAcapitalletterrepresentsadominantallele,andalowercaseletterrepresentsarecessiveallele??Figure14.5-PFigure14.5-PGeneticmakeup:PurpleflowersWhitePpFigure14.5-PGeneticmakeup:PurpleflowersFigure14.5-PGeneticmakeup:PurpleflowersWhitePpF1Geneticmakeup:PurplepPFigure14.5-PGeneticmakeup:PurpleflowersWhitePpF1Figure14.5-PGeneticmakeup:PurpleflowersWhitePpF1Geneticmakeup:PurplepPSpermfromF1(Pp)F2pPPEggsfromF1(Pp)plantp3:UsefulGenetic?AnorganismwithtwoidenticalallelesforaUsefulGenetic?Anorganismwithtwoidenticalallelesforacharacterissaidtobehomozygous純合forthegenecontrollingthatcharacterAnorganismthathastwodifferentallelesforageneissaidtobeheterozygous雜合forthegenecontrollingthatcharacterUnlikehomozygotes,heterozygotesarenottrue-breeding???Becauseofthedifferenteffectsofdominantandrecessivealleles,anorganism’straitsdonotalways?Becauseofthedifferenteffectsofdominantandrecessivealleles,anorganism’straitsdonotalwaysrevealitsgeneticcompositionTherefore,wedistinguishbetweenanorganism’sphenotype表型,orphysicalappearanceanditsgenotype基因型orgeneticmakeupIntheexampleofflowercolorinpeaplants,PPandPpplantshavethesamephenotype(purple)butdifferentgenotypes??Figure132Figure13211RatioRatioTheTestcross測?HowcanwetellthegenotypeofanindividualwithTheTestcross測?Howcanwetellthegenotypeofanindividualwiththedominantphenotype?SuchanindividualcouldbeeitherhomozygousdominantorheterozygousTheansweristocarryoutatestcross:breedingthemysteryindividualwithahomozygousrecessiveindividualIfanyoffspringdisplaytherecessivephenotype,themysteryparentmustbe???Figureunknowngenotype:PPorPp?parentisPPknowngenotype:parentisPppFigureunknowngenotype:PPorPp?parentisPPknowngenotype:parentisPpppppPPPpAlloffspringoffspringpurpleoffspringTheLawofIndependentTheLawofIndependent?MendelderivedthelawofsegregationbyfollowingasinglecharacterTheF1offspringproducedinthiscrossweremonohybrids單因子雜交,individualsthatareheterozygousforoneAcrossbetweensuchheterozygotesiscalledamonohybridcross???Mendelidentifiedhissecondlawofinheritancebyfollowingtwo?MendelidentifiedhissecondlawofinheritancebyfollowingtwocharactersatthesametimeCrossingtwotrue-breedingparentsdifferingintwocharactersproducesdihybridsintheF1generation,heterozygousforbothAdihybridcross,acrossbetweenF1dihybrids,candeterminewhethertwocharactersaretransmittedtooffspringasapackageorindependently??FigurePF1HypothesisofHypothesisofoffspringofFigurePF1HypothesisofHypothesisofoffspringofPhenotypicratioPhenotypicratioPhenotypicratioapproximately?Usingadihybridcross,?Usingadihybridcross,MendeldevelopedthelawofindependentassortmentThelawofindependentassortmentstatesthateachpairofallelessegregatesindependentlyofeachotherpairofallelesduringgameteformationStrictlyspeaking,thislawappliesonlytogenesondifferent,nonhomologouschromosomesorthosefarapartonthesameGeneslocatedneareachotheronthesamechromosometendtobeinheritedtogether???Concept14.2:ThelawsofConcept14.2:ThelawsofprobabilityMendelian?Mendel’slawsofsegregationandindependentassortmentreflecttherulesofWhentossingacoin,theoutcomeofonetosshasnoimpactontheoutcomeofthenexttossInthesameway,theallelesofonegenesegregateintogametesindependentlyofanothergene’salleles??TheMultiplicationandAdditionTheMultiplicationandAdditionAppliedtoMonohybrid?Themultiplicationrulestatesthattheprobabilitythattwoormoreindependenteventswilloccurtogetheristheproductoftheirindividualprobabilities相乘法則ProbabilityinanF1monohybridcrosscanbedeterminedusingthemultiplicationruleSegregationinaheterozygousplantislikeflippingacoin:Eachgametehasa?chanceofcarryingthedominantalleleanda?chanceofcarryingtherecessiveallele??FigureSegregationofallelesintoeggsSegregationofallelesintospermrRRRRFigureSegregationofallelesintoeggsSegregationofallelesintospermrRRRRrRrrrRr?Theadditionrulestatesthattheprobabilitythatanyoneoftwoormoreexclusiveevents?Theadditionrulestatesthattheprobabilitythatanyoneoftwoormoreexclusiveeventswilloccuriscalculatedbyaddingtogethertheirindividualprobabilities相加法則TheruleofadditioncanbeusedtofigureouttheprobabilitythatanF2plantfromamonohybridcrosswillbeheterozygousratherthanhomozygous?SolvingComplexGeneticsProblemswithSolvingComplexGeneticsProblemswithRulesof?WecanapplythemultiplicationandadditionrulestopredicttheoutcomeofcrossesinvolvingmultiplecharactersAdihybridorothermulticharactercrossisequivalenttotwoormoreindependentmonohybridcrossesoccurringsimultaneouslyIncalculatingthechancesforvariousgenotypes,eachcharacterisconsideredseparately,andthentheindividualprobabilitiesaremultiplied??FigureProbabilityofYYRR1/FigureProbabilityofYYRR1/4(probabilityofProbabilityof1/2Figure1/4(probabilityofFigure1/4(probabilityofpp)1/2(yy)6/16or1/21/41/21/21/21/41/21/41/2ChanceofatleasttworecessiveConcept14.3:InheritancepatternsaremoreConcept14.3:InheritancepatternsaremorecomplexthanpredictedbysimpleMendeliangenetics?TherelationshipbetweengenotypeandphenotypeisrarelyassimpleasinthepeaplantcharactersMendelstudied?ManyheritablearedeterminedbyonlyonegenewithtwoHowever,thebasicprinciplesofsegregationandindependentassortmentapplyeventomorecomplexpatternsofinheritance?ExtendingMendelianGeneticsforExtendingMendelianGeneticsfora?InheritanceofcharactersbyasinglegenemaydeviatefromsimpleMendelianpatternsinthefollowingsituations:WhenallelesarenotcompletelydominantorrecessiveWhenagenehasmorethantwoWhenageneproducesmultipleDegreesof?Completedominance完全Degreesof?Completedominance完全occurswhenphenotypesoftheheterozygoteanddominanthomozygoteareInincompletedominance不完全顯性,thephenotypeofF1hybridsissomewherebetweenthephenotypesofthetwoparentalIncodominance共同顯性twodominantallelesaffectthephenotypeinseparate,distinguishableways??PPPPF1PPTheRelationBetweenDominanceTheRelationBetweenDominance?Adominantalleledoesnotsubduearecessiveallele;allelesdon’tinteractthatAllelesaresimplyvariationsinagene’snucleotidesequenceForanycharacter,dominance/recessivenessrelationshipsofallelesdependonthelevelatwhichweexaminethephenotype???Tay-Sachsdiseaseisfatal;adysfunctionalenzymecausesanaccumulation?Tay-Sachsdiseaseisfatal;adysfunctionalenzymecausesanaccumulationoflipidsinthebrainAttheorganismallevel,thealleleisAtthebiochemicallevel,thephenotype(i.e.,theenzymeactivitylevel)isincompletelyAtthemolecularlevel,theallelesareFrequencyofDominant?DominantFrequencyofDominant?DominantallelesarenotnecessarilymorecommoninpopulationsthanrecessiveForexample,onebabyoutof400intheUnitedStatesisbornwithextrafingersor??2011PearsonEducation,?Theallelefor?ThealleleforthisunusualtraitisdominanttothealleleforthemorecommontraitoffivedigitsperappendageInthisexample,therecessivealleleisfarmoreprevalentthanthepopulation’sdominantallele?Multiple?MostgenesexistinpopulationsMultiple?Mostgenesexistinpopulationsinmorethantwoallelicforms?Forexample,fourphenotypesofthebloodgroupinhumansaredeterminedthreeallelesfortheenzyme(I)thatattachesAorBcarbohydratestoredbloodcells:IA,IB,andi.TheenzymeencodedbytheIAalleleaddstheAcarbohydrate,whereastheenzymeencodedbytheIBalleleaddstheBcarbohydrate;theenzymeencodedbytheialleleaddsneither?Figure(a)ThethreeallelesfortheABObloodgroupsandtheirFigure(a)ThethreeallelesfortheABObloodgroupsandtheiriAB(b)BloodgroupgenotypesandororRedbloodcellABOPleiotropy基因多效性?MostgenesPleiotropy基因多效性?Mostgeneshavemultiplephenotypiceffects,apropertycalledpleiotropyForexample,pleiotropicallelesareresponsibleforthemultiplesymptomsofcertainhereditarydiseases,suchascysticfibrosis囊胞性纖維癥andsickle-celldisease鐮刀型紅血球疾?MolecularGeneticsandGeneLocus:MolecularGeneticsandGeneLocus:7q31.2-TheCFTRgeneisfoundinregionq31.2onthelong(q)armofhumanchromosome7.GeneStructure:Thenormalallelicvariantforthisgeneisabout250,000bplongandcontains27mRNA:Theintron-freemRNAtranscriptfortheCFTRgeneis6129bplong.CodingSequence(CDS):4443bpwithinthemRNAcodefortheaminoacidsequenceofthegene'sproteinproduct.ProteinSize:TheCFTRproteinis1480aminoacidslongandhasamolecularweightof168,173ProteinFunction:ThenormalCFTRproteinproductisachloridechannelproteinfoundinmembranesofcellsthatlinepassagewaysofthelungs,liver,pancreas,intestines,reproductivetract,andskin.CFTRisalsoinvolvedintheregulationofothertransportpathways.AssociatedDisorders:Defectiveversionsofthisprotein,causedbyCFTRgenemutations,canleadtothedevelopmentofcysticfibrosis(CF)andcongenitalbilateralaplasiaofthevasdeferens???????ProteinCFTRcontrolschlorideionmovementProteinCFTRcontrolschlorideionmovementinandoutofthecell.?nandProteinFunctionProteinFunctionProteinStructureandCFTRtransportschlorideions(Cl-)ionsacrossProteinStructureandCFTRtransportschlorideions(Cl-)ionsacrossthemembranesofcellsinthelungs,liver,pancreas,digestivetract,reproductivetract,andskin.CFTRismadeupoffive??–twomembrane-spanningdomains(MSD1andMSD2)thatformthechlorideionchanneltwonucleotide-bindingdomains(NBD1andNBD2)thatbindandhydrolyzeATP(adenosinetriphosphate)andaregulatory(R)––DeltaF508,themostcommonCF-causingmutation,occursintheDNAsequencethatcodesforthefirstnucleotide-bindingdomain?ChangesinProteinChangesinProtein?CFTRfunctionsprincipallyasacAMP-inducedchloridechannelandappearscapableofregulatingotherionchannels.Besidesthemostcommonmutation,ΔF508,accountingforabout70%ofCFchromosomesworldwide,morethan850mutantalleleshavebeenreportedtotheCFGeneticAnalysisThesemutationsaffectCFTRthroughavarietyofmolecularmechanismswhichcanproducelittleornofunctionalCFTRattheapicalmembrane.??ExtendingMendelianGeneticsExtendingMendelianGeneticsforTwoMoreSometraitsmaybedeterminedbytwoormoregenes?2011PearsonEducation,Epistasis?Inepistasis,aEpistasis?Inepistasis,ageneatonelocusaltersthephenotypicexpressionofageneatasecondlocusForexample,inLabradorretrieversandmanyothermammals,coatcolordependsontwogenesOnegenedeterminesthepigmentcolor(withallelesBforblackandbforbrown)Theothergene(withallelesEforcolorandefornocolor)determineswhetherthepigmentwillbedepositedinthehair???FigureFigure:39:4EpistasisEpistasisInheritance多基因遺傳?QuantitativeInheritance多基因遺傳?QuantitativecharactersarethosethatvaryinthepopulationalongacontinuumQuantitativevariationusuallyindicatespolygenicinheritance,anadditiveeffectoftwoormoregenesonasinglephenotypeSkincolorinhumansisanexampleofpolygenicinheritance??FigureFigure8Numberdark-skin0156234NatureandNurture:TheNatureandNurture:TheImpacton?AnotherdeparturefromMendeliangeneticsariseswhenthephenotypeforacharacterdependsonenvironmentaswellasgenotypeThenormofreaction反應(yīng)范isthephenotypicrangeofagenotypeinfluencedbytheenvironmentForexample,hydrangeaflowers繡ofthesamegenotyperangefromblue-violettopink,dependingonsoilacidity??FigureBasicFigureBasicAcidic?Normsofreaction?NormsofreactionaregenerallybroadestforpolygeniccharactersSuchcharactersarecalledmultifactorialbecausegeneticandenvironmentalfactorscollectivelyinfluencephenotype?IntegratingaMendelianViewofIntegratingaMendelianViewofand?Anorganism’sphenotypeincludesitsphysicalappearance形態(tài)internalanatomy組織生理andbehavior行?Anorganism’sphenotypereflectsitsoverallgenotypeanduniqueenvironmentalhistoryConcept14.4:ManyhumanConcept14.4:ManyhumantraitsMendelianpatternsof?HumansarenotgoodsubjectsforgeneticresearchGenerationtimeistooParentsproducerelativelyfewBreedingexperimentsareHowever,basicMendeliangeneticsenduresasthefoundationofhuman?PedigreeAisafamilyPedigreeAisafamilytree家describestheinterrelationshipsofparentsandchildrenacrossgenerationsInheritancepatternsofparticulartraitscanbetracedanddescribedusing?FigureFForFigureFForb)Isanattachedearlobeadominantorrecessivetrait?(a)Isawidow’speakadominantorrecessivetrait??Pedigreescanalso?PedigreescanalsobeusedtomakepredictionsaboutfutureoffspringWecanusethemultiplicationandadditionrulestopredicttheprobabilityofspecificphenotypes?RecessivelyInherited?ManyRecessivelyInherited?ManygeneticdisordersareinheritedinarecessivemannerTheserangefromrelativelymildtolife-?TheBehaviorofRecessive?RecessivelyinheriteddisordersshowuponlyinindividualsTheBehaviorofRecessive?Recessivelyinheriteddisordersshowuponlyinindividualshomozygousfortheallele?Carriersareindividualswhocarrytherecessiveallelebutarephenotypicallynormal;mostindividualswithrecessivedisordersareborntocarrierisarecessive?Albinism白化characterizedbyalackofpigmentationinskinandhair?2011PearsonEducation,FigureaAAFigureaAAa?Ifarecessiveallelethatcausesadiseaseisrare,thenthe?Ifarecessiveallelethatcausesadiseaseisrare,thenthechanceoftwocarriersmeetingandmatingislow?Consanguineousmatings同族婚matingsbetweencloseincreasethechanceofmatingbetweentwocarriersofthesamerarealleleMostsocietiesandcultureshavelawsortaboosagainstmarriagesbetweenclose?CysticCysticfibrosisisthemostcommonlethalgeneticdiseaseCysticCysticfibrosisisthemostcommonlethalgeneticdiseaseintheUnitedStates,strikingoneoutofevery2,500peopleofEuropeanThecysticfibrosisalleleresultsindefectiveorabsentchloridetransportchannelsinplasmamembranesleadingtoabuildupofchlorideionsoutsidethecellSymptomsincludemucusbuildupinsomeinternalorgansandabnormalabsorptionofnutrientsinthesmallintestine???Sickle-CellDisease:AGeneticDisorderSickle-CellDisease:AGeneticDisorderEvolutionary?Sickle-celldiseaseaffectsoneoutof400ThediseaseiscausedbythesubstitutionofasingleaminoacidinthehemoglobinproteininredbloodcellsInhomozygousindividuals,allhemoglobinisabnormal(sickle-cell)Symptomsincludephysicalweakness,pain,organdamage,andevenparalysis???Fig.14-?Heterozygotes(saidtohavesickle-celltrait)areFig.14-?Heterozygotes(saidtohavesickle-celltrait)areusuallyhealthybutmaysuffersomesymptomsAboutoneoutoftenAfricanAmericanshassicklecelltrait,anunusuallyhighfrequencyofanallelewithdetrimentaleffectsinhomozygotesHeterozygotesarelesssusceptibletothemalariaparasite,sothereisanadvantagetobeingheterozygous??DominantlyInherited?SomehumanDominantlyInherited?SomehumandisordersarecausedbydominantallelesDominantallelesthatcausealethaldiseasearerareandarisebymutationAchondroplasia軟骨發(fā)育不全isaformofdwarfismcausedbyararedominant??FigureDdFigureDdddHuntington’sDisease:ALate-Onset?TheHuntington’sDisease:ALate-Onset?Thetimingofonsetofadiseasesignificantlyaffectsitsinheritance?Huntington’sdiseaseisdegenerativediseaseofthenervousThediseasehasnoobviousphenotypiceffectsuntiltheindividualisabout35to40yearsofOncethedeteriorationofth