6 IMGT standardization for alleles and mutations of the V-LIKE ...
LT 1 - I can explain the relationships among alleles, genes, … · 2018-03-15 · variety of...
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Pre-AP Biology 2017-2018 Unit 7 Genetics Review Outline LT 1 - I can explain the relationships among alleles, genes, chromosomes, genotypes, and phenotypes. This target covers application of the vocabulary words above. Study your completed vocabulary list assignment and refer to the diagrams below.
Transcript of LT 1 - I can explain the relationships among alleles, genes, … · 2018-03-15 · variety of...
Pre-APBiology2017-2018
Unit7GeneticsReviewOutlineLT1-Icanexplaintherelationshipsamongalleles,genes,chromosomes,genotypes,andphenotypes.
Thistargetcoversapplicationofthevocabularywordsabove.Studyyourcompletedvocabularylistassignmentandrefertothediagramsbelow.
LT2-IcansummarizetheworkofGregorMendelandthegeneticprinciplesthatarosefromthatwork.• GregorMendelwasamonkthatstudiedpeaplantbreedinginthe1800’s
o Firstpersontohavecorrectideasaboutinheritanceo Experimentstookeightyears(1856-1863)andresultswerepublishedin1865.
• Usedpeaplantsashismodelorganismbecausetheygrewquicklyandwereeasytostudybecauseoftheirvarietyoftraits(roundvwrinkled,yellowvgreen,tallvshort)
o Hegrewover10,000peaplants,keepingtrackofprogenynumberandtype.o Mendelfiguredoutthatgenescomeinpairsandareinheritedasonefromeachparent.o Trackedthesegregationofparentalgenesandtheirappearanceintheoffspringasdominantor
recessivetraits.• Mendelconductedcrossesoftrue-breeding(homozygous)parentstoproduceaheterozygousF1generation,
whichwerethencrossedbacktothemselves(F1xF1)toproduceanF2generationthatshowedagenotypicrationof1:2:1.
• Mendel'sLawsofHeredity:
1)TheLawofSegregation:Eachtraitisinheritedbyagenepair.Parentalgenesarerandomlyseparatedsothatsexcellscontainonlyonegeneofthepair(meiosis).Offspringthereforeinheritonegeneticallelefromeachparentwhensexcellsfertilize.2)TheLawofIndependentAssortment:Genesfordifferenttraitsaresortedseparatelyfromoneanothersothattheinheritanceofonetraitisnotnecessarilydependentontheinheritanceofanother.3)TheLawofDominance:Anorganismwithalternateformsofagenewillexpresstheformthatisdominant.
LT3–IcancompleteMendeliangeneticsPunnettsquarequestions• MendelianPunnettSquaresfollowtheLawofDominance–onealleleisdominantandtheotherisrecessive.
Therecessivephenotypeisonlydisplayedbyanorganismwithahomozygousrecessivegenotype.o EXAMPLE:o DominantPhenotypecanbeAAorAaforgenotypeo RecessivePhenotypecanonlybeaa
• Monohybridcrossesshowthepossibleoffspringinacrossofonetrait.§ Genotypeprobabilitycanbe0outof4(0%),1outof4(25%),2outof4(50%),or4outof4
(100%)§ Phenotypeprobabilitycanalsobeanyoftheabove,orexpressedasaratio.
• Dihybridcrossesshowtheprobabilityofoffspringinacrossoftwotraits.§ Probabilityisnowoutofatotalof16.§ WATCHTHEAMOEBASISTERSVIDEOIFYOUSTILLARESTRUGGLETOSETUPTHESE
PROBLEMS!
LT4–IcancompleteNon-MendelianPunnettSquarequestions.
• Non-Mendelianinheritancereferstotraitsthatdonotfollowstandarddominant-recessivepatterns.Thisincludes:
o IncompleteDominance:Truebreedingphenotypesarehomozygous;heterozygousgenotypeproducesnewphenotypethatisanintermediate,ormixture,ofthetwo.Example:aredflowerisrepresentedbyRR,awhiteflowerisrepresentedbyWW,andtheheterozygousRWappearsaspink.
o Codominance:Someallelescanbeequallyexpressedwhenbothpresent,forexampleinhowtheAproteinandBproteinarecodominantinbloodtypesuchthataTypeABindividualexpressesbothproteins.Anotherexamplecouldbetheflowercolorscenario,whereredisRR,whiteisWW,andRWisred-and-whitesplotches.
o Epistatis:Theexpressionofsometraitsisdeterminedbygenesthatcan“turnon”and“turnoff”thephenotype,thisiscalledepistatis.Forexample,alpacascanbeblackortanintermsofwoolcolor,butthereisanothergenethatcontrolswhetherornotpigmentinthewoolappearsatall.
o Sex-Linked:SometraitsarelocatedontheXorYsex-chromosomesandthereforeareconsidered
sex-linked.Thegenderoftheindividualdetermineshowmanycopiesofthealleleanindividualinherits.RememberfemalesareXXandmalesareXY.
o Polygenic:Sometraits,suchaseyecolororheightinhumans,areinfluencedbymanygenesworkinginconjunction.Thisproducesawidearrayofpossiblephenotypes(i.e.therearemanydifferentshadesofbrowneyes).
LT5-Icansummarizehowgeneticabnormalitiescancausedisordersinanorganism,suchasnondisjunction.
• GeneticdisordersarecausedbymutationswithintheDNAsequences(substitutionorframeshiftmutations)orbyachromosomalabnormality(nondisjunction)
o Point/SubstitutionMutationExamples:Tay-SachsDisease,Hemophilia,Sickle-CellAnemiao ChromosomalAbnormalityExamples:DownSyndrome(Trisomy21),TurnerSyndrome(Monosomyx),
KlinefelterSyndrome(TrisomyXXY)• Nondisjunctionisthefailureofchromosomestoproperlyseparateduringgameteformationinmeiosis.This
resultsingameteswiththeimpropernumberofchromosomes(usuallyhavingoneextraoronemissing,n+1orn-1).
o ThiscanresultinTrisomy(3chromosomesinsteadof2ataspecificlocation)orMonosomy(1chromosomeinsteadof2ataspecificlocation).
o Itispossibletohavemorethan3chromosomesatalocation,butthisisuncommon.
• Chromsomalabnormalitiescanbeassessedusingakaryotype,whichisapictureofallchromosomesarrangedbylargesttosmallestandnumbered,withthesex-chromsomesappearinglast.Humanshave23pairs–1through22areautosomal(notsex-related)andthelastpairarethesexchromosomes(XXorXYinanormalindividual).
LT6–Icananalyzeapedigreecharttodeterminemodeofinheritanceforagiventrait.• Ahumanpedigreeshowsthepatternofinheritanceofatrait/geneacrossgenerations• Malesarerepresentedbysquaresandfemalesarerepresentedbycircles• Individualswiththetrait/genearecoloredinandthosethatdonothaveitareleftblank• Forrecessivetraits,known“carriers”wouldbehalfshaded• Genesarelocatedondifferentchromosomes:
o AutosomalInheritance:gene/traitisunrelatedtogender,NOTonasex-chromosome(effectsmalesandfemalesequally)
o Sex-LinkedInheritance:gene/traitisinheritedfromeithertheXortheYsexchromosome(effectseithermalesorfemalesmore)
• Manypatternsofinheritance,butforthisclassyoushouldknow:
Pa#ern 1: Autosomal Dominant • Onlyonecopyofadiseasealleleisnecessaryforanindividualtoexpressthephenotype.• Malesandfemalesaffectedequally.• Allaffectedindividualswillhaveatleastoneparentwhocarriesthediseaseallele.
Pa#ern 2: Autosomal Recessive • Twocopiesofadiseasealleleisnecessaryforanindividualtoexpressthephenotype.• Malesandfemalesaffectedequally.• Theparentsofanaffectedindividualmaynotaffectedbutaregenecarriers.
Pa#ern 3: X-Linked Dominant • OnlyonecopyofadiseasealleleontheXchromosomeisnecessaryforanindividualtoexpressthephenotype.• Malesandfemalesaffectedequally.• Whenafemaleisaffected,thereisa50%chancefortheoffspringtoinheritthediseaseallele.Whenamaleisaffected,allhisdaughterswillbeaffected,butnoneofhissonswillbeaffected.
Pa#ern 4: X-Linked Recessive • TwocopiesofadiseasealleleontheXchromosomeisnecessaryforafemaletoexpressthephenotype,butonlyonecopyforamalesincethealternateYchromosomedoesnotinfluenceX-linkedtraits.
• Malesaffectedmorefrequentlythanfemales.
• Affectedmalestransmitthediseasealleletoalloftheirdaughters,whoarethencarriers,buttononeoftheirsons.
• Womenareaffectedwhentheyhavetwocopiesofthediseaseallele.Alloftheirsonswillbeaffected,andalloftheirdaughterswillbeunaffectedcarriers.
