final gene-ius study guide · 2020-01-20 · updated: january 2019 1 gene-ius study guide this...
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GENE-iusStudyGuide
ThisstudyguideisintendedtohelpGENE-iuscoachesunderstandthetopicstheeventwillcoverandthelevelofcomprehensionexpectedforthosetopics.Itisrecommendedandexpectedthatadditionalmaterials,websitesandactivitiesbeusedtohelppreparetheteamsforthisevent.
I. BasicCell/MolecularBiology–Studentsshouldonlyfocusonthefollowingbasicconceptsofeukaryotic(willsticktoanimal)cells.
A. Partsofthecell
1. Whatisacell?–Acellisthebasicunitoflife.Alllivingthingsaremadeupofonecell(likebacteriaoryeast)ormanycells(likehumans).Eachcellislikeaminifactorywithindividualparts(organelles)workingtogethertocarryoutspecificfunctions.
2. Cellmembrane–Thecellmembraneistheoutermostlayerofthecell.Itislikeabagthatholdseverythingtogether.Itcontainsopeningsthatallowthingstoenterandleavethecell.Itisliketheshippingandreceivingdepartmentinthecellfactory.
3. Cytoplasm–Thecytoplasmisaliquidsubstancethatfillsupthespaceinsidethemembrane.Itholdsalltheotherorganellesofthecellinplaceandhelpsgivethecellshape.Itislikethebusyfactoryfloorwiththingsmovingabout.
4. Nucleus–Thenucleusisthe“brains”ofthecell.Itisthecontroloffice.Ithousesthegeneticmaterialofthecell(DNA/genes/chromosomes).Ithasitsownmembrane,thenuclearmembrane.
5. Ribosomes-The“workers”ofthecellfactory.RibosomesusetheinstructionsstoredinDNAtoassembleproteins.Proteinsarethebuildingblocksandmachinesthecellusestocarryoutitsmanyfunctions.
RIBOSOME
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http://www.ducksters.com/science/the_cell.php http://www.biology4kids.com/files/cell_main.html
B. BasicMolecularBiology
1. DNA(deoxyribonucleicacid)–ADNAmoleculecontainstwolongstrandswoundtogethertoformadoublehelix.Eachstrandhasa“backbone”madeupofphosphateanddeoxyribose(asugar).Extendingfromthisbackbonearefourpossiblebases;adenine(A),thymine(T),cytosine(C)orguanine(G).Aphosphate,adeoxyriboseandabasemakeupanucleotide.NucleotidesarethebasicbuildingblocksofaDNAmolecule.EachstrandoftheDNAmoleculeislikehalfofaladderwithnucleotidesstackedupontopofeachother.ThetwostrandsofDNAareheldtogetherbytheinteractionor“basepairing”ofthesenucleotides.
a) Basepairingrule–adeninewillonlypairwiththymine(A-T)andguaninewillonlypairwithcytosine(G-C).
b) Antiparalleldoublehelix–Antiparallelisatermthatmeansyouhavetwostrandsthataresidebysidebutruninoppositedirections.ADNAmoleculeiscomprisedoftwostrandsthatarewoundtogetherandjoinedbythebasepairingofthenucleotidesbuteachofthetwostrandsrunsindifferentdirections.TheendofaDNAstrandthathasthephosphateisreferredtoasthe5’(5prime)end.Theendofthatstrandwithasugar(deoxyribose)isreferredtoasthe3’(3prime)end.Inthediagramsbelow,youcanseethatonestrandruns5’to3’whilethecomplementarystrandruns3’to5’.
Teamsdonotneedtounderstandthechemicalstructurethatresultsinthe designationoftheendsas5’or3’.
c) DNAstructureidentification(AppendixA)–Studentsshouldbeabletoidentifythemajorpartsdescribedinthisstudyguide.Theyshouldbepreparedtolabeladiagramoridentifypartsona3Dmodel.StudentsarenotexpectedtounderstandthechemicalstructureofDNAbeyondwhatisdescribedabove.
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2. Genes–AgeneisaspecificsectionofDNAthatcontainsalltheinformationor“code”tomakeaspecificprotein.Proteinsarelikemachinesthatworktogethertocarryoutallthefunctionsacellneedstogetdonetostayalive.Eachproteinismadeupofaminoacidsarrangedinaspecificorder.Thespecificorderoftheaminoacidsinaproteiniscodedbythespecificsequenceofthenucleotides,A,C,G,andTinthegeneforthatprotein.IfthereisachangeintheDNAsequenceinageneorpartofthesequenceismissingitcansometimescausewhatisreferredtoasamutation.Forexample,iftheDNAsequenceforaspecificgenehasanA(adenine)whereitissupposedtohaveaC(cytosine),theinstructionswillbewrongandthecellwillformadefective“part”orprotein.(Seesicklecelldiseasebelow)
http://www.ducksters.com/science/biology/dna.php
a) CodonReading–TheDNAcodeofaspecificgeneisread3nucleotidesatatimeorasatriplet.Thesetripletsarecalledcodons.Eachcodoncorrespondstoaspecificaminoacid.Individualaminoacidsarethebuildingblocksofproteins.Thinkofageneasalongsentencemadeupof3letterwords.Eachwordcorrespondstoaspecificaminoacid.Theseaminoacidsarethenstrungtogetherinaspecificordertomakeaspecificprotein.Thereisevenacodonthatrepresentsa“stop”inthesequence,whichisanalogoustoaperiod.AlthoughthefullgeneforaproteincontainsadditionalDNAsequencesthe“coding”sequencereferstothatportionthatspecificallycodesfortheaminoacidsoftheprotein.ThiscodingsequencewillstartwiththecodonATG,thecodonfortheaminoacidMethionine.AppendixBcontainstheactualDNAcodontablethestudentswillbegivenduringtheevent.Italsocontainsseveralexamplesofgenesequencesandthecorrespondingaminoacidsequenceoftheproteinthatsequencewouldproduce.Noticethatseveralcodonsrepresentthesameaminoacidsandthereare3separatestopcodons.Forthesakeofsimplicity,whenthetermgeneisusedinthiseventitisreferringtothecodingsequenceportionofthegene.5thgradeonly–Pleasesee“transcription”formoredetailedinformationaboutcodonreadingandRNA.
b) Mutations–Asmentionedabove,ifanucleotidesequenceofageneischangeditmayresultinamutation.Themutationiscausedbecausethatnucleotidechangemayresultinadifferentcodon,whichwillthenresultindifferentaminoacidbeingplacedatthatpositionintheprotein.Sometimes,onesingleaminoacidchangeinaproteincanresultinacompletelyorpartiallydefectiveprotein.Thisisthecaseforthegeneticdiseaseinhumansknownassicklecelldisease.Sicklecelldiseaseaffectsmillionsofpeopleworldwideandaffects70,000to80,000Americans.Peoplewithsicklecelldiseasehaveamutationinhemoglobin,aproteinfoundinredbloodcellsandnecessarytodeliveroxygentoallthecellsthroughoutthebody.Thedefectivehemoglobinwillstarttoclumptogetherundersomeconditionscausingtheredbloodcellstoformasickleshape.Thesesickledredbloodcellscandieleadingtoaconditionknownasanemiaorthesesicklecellsmaygetstuckinthesmallbloodvesselsresultinginpainandotherseriousmedicalcomplications.Thisgeneticdiseaseiscausedbyasinglenucleotidechangeresultinginanaminoacidchangeinthehemoglobinprotein(seebelow).Studentsdonotneedtoknowthemedicaldetailsofsicklecelldisease.Itistoserveasareallifeexampleofageneticmutation.
http://kidshealth.org/en/teens/sickle-cell-anemia.html
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GeneticmutationcausingSickleCellDisease
c) Typesofmutations
(1) Missense–asinglenucleotidechangethatresultsinthesubstitutionofoneaminoacidforanotherintheproteinmadebythegene.Amissensemutationmayormaynotresultinadefectiveprotein.Itdependsonthetypeofaminoacidbeingchangedandthelocationofthataminoacidintheprotein.Thesicklecellexampleaboveisamissensemutation.Teamswillnothavetodeterminetheimpactofanaminoacidchange.
(2) Synonymous-asinglenucleotidechangethatdoesnotresultinanaminoacidchangeinthefinalproteinduetotheredundancyinthegeneticcode(multiplecodonscodeforthesameaminoacid).
(3) Nonsense–asinglenucleotidechangeintheDNAsequenceofageneresultinginacodonforastopsignal.Thistypeofmutationresultsinashortenedproteinthatmayfunctionimproperlyornotatall.
(4) Frameshiftmutations-Frameshiftmutationsareduetoeitherinsertionsordeletionsofnucleotidesinthecodingregionofthegene.Whenoneormorenucleotidesareeitherinsertedordeletedthereisachangeinthegene'sreadingframe.Areadingframeisthesequenceofcodonsinthegenethatcorrespondtothespecificsequenceofaminoacids.Thus,frameshiftmutationsmayalterallofthecodonsthatoccurafterthedeletionorinsertion.Theresultingproteinisusuallynonfunctional.
https://ghr.nlm.nih.gov/primer/mutationsanddisorders/possiblemutations
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3. CentralDogmaofMolecularBiology(5thgradeonly)
a) TheDNAwithinagenecontainstheinformationonhowtojoinspecificaminoacidstogethertoformaprotein.TheinformationcontainedintheDNAisdeliveredtotheproteinmakingmachinery(ribosomes)throughanintermediatemessengercalledribonucleicacid(RNA).RNAandDNAaresimilarmolecules.
b) RNA-ThereareacoupleofkeydifferencesbetweenDNAandRNAmolecules.Theycontaindifferentsugars.DNAhasadeoxyribosesugarwhileRNAhasaribosesugar.Whilethreeoftheirfournitrogenousbasesarethesame,RNAmoleculeshaveabasecalleduracil(U)insteadofathyminebase.Uracilreplacesthepositionofthymineandformscomplementarypairswithadenine.DNAisadoublestrandedmoleculewhileRNAispredominatelyasinglestrandedmolecule.Finally,DNAisfoundinthenucleusofacell(alsointhemitochondriabuttheydon’tneedtoknowthat)whileRNAcanbefoundinthenucleus,cytoplasmandribosomes.
https://www.diffen.com/difference/DNA_vs_RNA
c) TranscriptionistheprocesswheretheinformationstoredasDNAinageneistransferredintoRNA.ThisRNAmoleculecanthencarrythisinformationoutofthenucleusandintothecytoplasm.Inthecytoplasm,ribosomescombinewiththeRNAmoleculeinordertoconvertthisinformationintoaprotein.Thisprocessisknownastranslation.Duringtranslation,geneticinformationisreadascodonstoassembleaminoacidsinaspecificsequencetoformaprotein.
ThereareseveraltypesofRNAmolecules.TheRNAgeneratedduringtranscriptionis messengerRNAormRNA.TeamsdonotneedtoknowthedifferencesbetweenRNA types.
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Onlytheterms“codingstrand”and“templatestrand”willbeusedintheevent.5thgrade teamsshouldunderstand:theDNAtemplatestrandisusedtogeneratetheRNAmolecule. https://basicbiology.net/micro/genetics/transcription-and-translation/ https://www.atdbio.com/content/14/Transcription-Translation-and-Replication
4. Chromosomes–AlloftheDNAinthenucleusofacellistightlypackagedintostructurescalledchromosomes.Humanshave23differentchromosomespairs.Mosthumancellshaveatotalof46chromosomesbecausetheyhavetwocopiesofeachchromosome,onefromtheirmotherandonefromtheirfather.Thesetwoversionsofthesamechromosomearecalledhomologouschromosomes.Twenty-twoofthechromosomesarecalledautosomesandarenumbered1to22.The23rdpairofchromosomesrepresentsthesexchromosomes,XorY.Ifyouareafemale,youwillhavetwoXchromosomes.Ifyouareamale,youwillhaveoneXandoneYchromosome.
3’…TACCGGACCTGAACT…5’
5’…ATGGCCTGGACTTCA…3’DNA
CodingStrand(alsoknowas:senseortopstrand)
TemplateStrand(alsoknowas:antisenseorbottomstrand)
5’…AUGGCCUGGACUUCA…3’RNA
Methionine–Alanine–Tryptophan–Threonine–Serine-….Protein
Transcription
Translation
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http://kidshealth.org/en/kids/what-is-gene.html http://kidshealth.org/en/parents/about-genetics.html
5. ChromosomeMorphologyandIdentification–Chromosomesdifferinsize,centromereposition,armlengthandstainingpattern.Inordertoidentifyindividualchromosomes,somecellsarecollectedandallowedtodividesothattheycanbeanalyzedatacertainpointduringmitosis.Thechromosomesarestainedwithspecialchemicalsandviewedunderamicroscope.Everychromosomehasacentromere(thepointwherethemitoticspindleattaches)andthechromosomestrandextendingfromthecentromereisreferredtoasanarm.Theshortarmislabeledp(forpetite)andthelongarmislabeledq(becauseqfollowspinthealphabet).Ifthecentromereisinthecenterofthechromosome,itiscalledmetacentric.Ifthecentromereislocatednearoneendofthechromosomeitiscalledacrocentric.Thethirdcentromerepositionmaybebetweenthecenterandtheendofthechromosomeandiscalledsubmetacentric.Chromosomescanalsobeidentifiedbytheiruniquebandingpatternwhentheyarestained.ThemostcommonstainisGiemsastain,whichresultsinwhatiscalledaGbandingpattern.Finally,chromosomescanalsobedistinguishedbytheiroverallsize.
Humanchromosomesstained withGiemsa(Gbanding)
6. KaryotypeAnalysis–Doctorsandgeneticistscanevaluatethenumberandconditionofanindividual’schromosomesbyassessingtheirkaryotype.Akaryotypeisthenumber,sizeandshapeofanindividual’schromosomes.Anindividual’skaryotypeisoftendisplayedasakaryogramwhichisaphotographoftheindividual’sstainedchromosomesarrangedintopairsfrom1to22followedbythesexchromosomes,XandY.Individualchromosomesareidentifiedbycomparingtheirsize,shapeandbandingpatterntoideograms,whicharediagrammaticrepresentationofthestainedchromosomes.Karyotypeanalysisisdonetoidentifygrosschromosomeabnormalitieslikemissingchromosomes,extrachromosomesorbrokenchromosomes.
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Karyograms
a) Monosomy–Monosomyisthetermforamissingchromosome.Anormalhumanshouldhavetwoofeveryautosomeandapairofsexchromosomes(XXorXY).Sometimesduringmeiosis(seebelow),amistakeismadeandonechromosomegetsleftbehind.Thehumanthatdevelopsfromthiseggorspermwouldbemissingoneofthepair.Mostfullchromosomemonosomyabnormalitiesarelethalinhumans.TheexceptionisTurnerssyndromeor45,Xwhichisnotlethal.AfemalewithTurnerssyndromemayhaveseveralphysicalabnormalitiesandisunabletoreproduce.
b) Trisomy–Trisomyisthetermforhavinganextrachromosome.Again,natureisnotperfectandsometimesaneggorspermisproducedwithanextrachromosome.ThemostcommonformofthistypeofgeneticdefectisTrisomy21orDownsyndrome.IndividualswithDownsyndromecanhaveavarietyofhealthconditions,intellectualdisabilitiesandcharacteristicfacialfeatures.
Teamsdonotneedtounderstandanyofthemolecularmechanismsthatresultinchromosomalabnormalities(nondisjunction).SomekaryotypesshowchromosomesthatlooklikeX’s.ThisoccurswhenthechromosomesareisolatedafterDNAreplicationbutbeforetheindividualchromatidshaveseparated.Iwillonlyusesinglechromatidkaryotypesliketheoneshownabove.Teamsshouldfocusonunderstandingwhatanormalhumankaryotypeshouldlooklikeandidentifyingdifferencesbetweenanormalhumankaryotypeandanabnormalone.Ifshownakaryotypethatismissingachromosome#2,theyshouldbeabletosayitisabnormalandthedefectismonosomy2.
c) Karyotypeanalysis(AppendixCandMagneticChromosomeKit)–Studentsmaybeaskedtolookatakaryogramandanswersomebasicquestionsaboutit.
http://www.slideshare.net/saimamansoorbugvi/karyotypes-and-karyotyping-15649528
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C. Celldivision
1. Mitosis–Asyougrow,yourcellsdivideandmakemorecells,makingyoubiggerandbigger.Asyouage,yourcellsalsodividetoreplaceoldcellswithneweronesortoreplacedamagedcells.Theprocessofonecelldividingintotwonewidenticalcellsiscalledmitosis.Priortothestartofmitosis,allthechromosomesinacellareduplicated.Duringmitosisthesechromosomesendupinthetwonewcellsthatareproduced.Theoriginalcell(ifhuman)willhaveatotalof46(remember,23differentonesbutoneeachfromthemotherandfather).Aftermitosis,youwillhavetwonewcells(“daughtercells”)eachwithidenticalcopiesoftheoriginal46chromosomes.
2. Meiosis–Theprocessofmeiosisincludestwocelldivisionsinwhichyoustartwithonecellwith46chromosomes(ifhuman)andendupwith4cellswith23chromosomes.Meiosisisusedtocreatesexcells(gametes,spermoregg).ThesecellshaveonlyIcopyofeachofthe23chromosomes.Whentheyarejoinedtogetherduringfertilizationtheresultingcellwillhave46chromosomes,23chromosomesfromthemotherand23chromosomesfromthefather.
Teamsdonotneedtoknowthestepsinvolvedintheprocessofmitosisormeiosis (prophase,anaphase,etc.).Theydonotneedtounderstandtheconceptofcrossing overinmeiosis. http://www.ducksters.com/science/biology/cell_division.php http://www.biology4kids.com/files/cell2_mitosis.html https://www.youtube.com/watch?v=f-ldPgEfAHI&t=310s https://www.youtube.com/watch?v=toWK0fIyFlY
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II. ClassicalGenetics–TeamsshouldonlyfocusonthefollowingbasicconceptsofclassicalorMendeliangenetics
A. TraitsandHeredity
1. Traitsarephysicalcharacteristicssuchaseyecolor,heightortheabilitytodance.Sometraitscanbeinfluencedbyanindividual’sbehaviororenvironment.Forexample,ifyouspendalotoftimeinthesun,thenyourskincolormaybecomedarkeroryoucanbecomeadancerbytrainingandpractice.Othertraitsareconsideredinheritedorgenetictraitsandaredeterminedbythegenesyouinheritfromyourparents.Forexample,youhaveblueeyesfromyourparentsorredhairfromyourgrandparents.
2. Heredityisthepassingoftraitsorphysicalcharacteristicsfromonegenerationtothenext(parentstochildren).
Teamsshouldunderstandthedifferencebetweenatraitthatisinheritedandonethatcan beinfluencedbytheenvironment.
B. Genes,Alleles,PhenotypesandGenotypes
1. AgeneisaparticularsequenceofDNAthathastheinstructionsforaparticularprotein.Thereareusuallyseveraldifferentversionsor“alleles”foragene.Forexample,thereisageneforeyecolorbutyoucanfindseveralallelesfortheeyecolorgenesuchasblueorbrown.(note-thegeneticsofeyecolorismuchmorecomplicatedbutwewanttokeepthingssimplehere).
2. Ingenetics,werefertothephysicalappearanceormake–upofanorganismasthephenotype.Whatyoulooklikeorwhetherornotyouhaveaparticularconditionwouldbeyourphenotype.
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3. Anindividual’sgenotypereferstotheirgeneticmake-up.Specifically,itisthetwoallelesthatyouinheritedfromyourparents.
a) homozygous–anindividualissaidtohaveahomozygousgenotypeifthetwoallelestheycarryarethesame
b) heterozygous–anindividualissaidtohaveaheterozygousgenotypeifthetwoallelestheycarryaredifferent
C. Dominantvs.Recessive
1. Ifwejustfocusonsimplepatternsofinheritance,thenwecanrefertodifferentversionsofallelesasbeingdominantorrecessive.
a) Adominantallelewilldetermineanindividual’sphenotyperegardlessofwhetherthatindividualishomozygousorheterozygousforthatallele
b) Arecessiveallelewillonlybeexpressedinthephenotypeofanindividualifthatindividualishomozygousforthatallele.Ifanindividualisheterozygous,withonedominantandonerecessiveallele,thedominantallelewinsandthatisthetraitthatyouwillseeinthephenotype.
c) Nomenclature–Forthepurposesofthisevent,geneswillbedenotedbythefirstletterofthedominantalleleforthattrait.Forexample,thealleleforaflowerwhosedominantcoloriswhitewouldberepresentedby“w”.ThedominantallelewouldberepresentedbyacapitalWandtherecessiveallelewithalowercasew.Aflowerthatishomozygousrecessivewouldhavethegenotypewwbutcouldbered.
2. PleaseseeappendixDforanexampleofhowthesegenetictermsworktogether.
D. PunnettSquares
1. Oneofthebenefitsofstudyinggeneticsisthatitallowsustopredictthelikelihoodofinheritingparticulartraits.Thisisveryhelpfulforplantandanimalbreedersandcanevenbeusedinhumanstohelpdeterminethechancesofhavingachildwithaparticulargeneticcondition.ThesimplestwaytodothisisbysettingupaPunnettsquare.APunnettsquareisagraphicalwaytosetupahypotheticalcrossorbreedingbetweentwoparentsanddetermineallthepossiblegeneticcombinationsorgenotypesoftheoffspring.
2. PleaseseeappendixEforaguidetosettingupandinterpretingPunnettsquares.Onlymonohybrid(singletrait)crosseswillbeused.Teamswillbeexpectedtosetupcrossesbasedontheinformationgivenaboutaparticulartraitandtheparentsandinterprettheresults.
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E. PedigreeCharts,AnalysisandPatternsofInheritance
1. Wecanbetterunderstandtheinheritancepatternofageneticdiseasewithinafamilybydoingapedigreeanalysis.Thisinvolvescollectinginformationaboutaparticulardiseasefromasmanyrelativeswithinafamilyaspossibleandconstructinga“familytree”orpedigreechart.Apedigreechartusessymbolsandlinestorepresentpeopleandrelationshipsandmakesiteasiertovisualizetherelationshipswithinfamilies.Withthisinformation,geneticistscanidentifytheinheritancepatternofaparticularconditionanddeterminetheriskofafamilymemberinheritingit.
2. AutosomalDominantandAutosomalRecessive
Bothgradesmustunderstandautosomaldominantandautosomalrecessiveinheritancepatterns.Atraitwillhaveanautosomaldominantinheritancepatternwhenonlyonecopyofitisnecessaryfortheindividualtohavethephenotypeassociatedwiththattrait.Atraitwillhaveanautosomalrecessiveinheritancepatterniftwocopiesarenecessaryforanindividualtohavethephenotype.
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3. Xlinkedrecessive(5thgradeonly) ForatraittohaveanXlinkedrecessiveinheritancepatternthegeneforthetraitmustfirstbe locatedontheXchromosome.SincefemaleshavetwoXchromosomes,anXlinkedrecessive traitwillonlybepresentinfemaleswhentheyhavetwoallelesforthattrait.However,males onlyhaveoneXchromosomesotheywillhavethephenotypeforthistraitwithonlyonecopy ofthatallele.MalesareaffectedbyX-linkedrecessivedisordersmuchmorefrequentlythan females.AcharacteristicofX-linkedinheritanceisthatfatherscannotpassX-linkedtraitsto theirsons(nomale-to-maletransmission).
4. PleaseseeappendixFforaguidetosettingupandinterpretingpedigreecharts.Teamswillbeaskedtoidentifyandunderstandthecomponentsofthepedigreechartaswellasidentifytheinheritancepatternforthetrait.
https://www.brainpop.com/health/geneticsgrowthanddevelopment/heredity/ http://anthro.palomar.edu/mendel/mendel_2.htm http://www.dnaftb.org http://www.sciencebuddies.org/science-fair-projects/project_ideas/Genom_p010.shtml-background
F. HumanABOBloodTypes–ExampleofCo-dominanceandMultipleAlleles
1. Wehavetalkedaboutallelesbeingdominantorrecessivetoeachother.Thisisnotalwaysthecase.Manytimestherearemultiplealleleoptionsforaparticulargenealthoughyouwillneverinheritmorethantwo.Inaddition,therearetimeswhenbothofthetwoallelesyouinheritareexpressedtogetherresultinginaphenotypethatisacombinationofthetwo.Thisisreferredtoasco-dominant.ThehumanABObloodtypegroupsareanexampleofco-dominanceandmultiplealleles.
2. Humansareassignedtoabloodgroupbasedonthepresenceorabsenceofspecificantigensor“markers”ontheirredbloodcells.Therearethreepossiblealleles,A,BorO.BothAandBallelesaredominantoverO.Asaresult,individualswhohaveanAOgenotypewillhaveanAphenotype.PeoplewhoaretypeOhaveOOgenotypes.Inotherwords,theyinheritedarecessiveOallelefrombothparents.TheAandBallelesareco-dominant.Therefore,ifanAisinheritedfromoneparentandaBfromtheother,thephenotypewillbeAB.
3. AppendixGshowsadetaileddescriptionofthehumanbloodgroupgenotypesandphenotypes.
http://anthro.palomar.edu/blood/ABO_system.htm Note:Someofthecrossesandpedigreestheteamswillbegivenmaybehypotheticalor simplifiedinordertopreventanyconfusionandtofocusonthebasicconceptsofinheritance patterns.
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III. HumanGeneticDiseasesandConditions
A. Pleasebesensitivewhendiscussinggeneticdiseasesandconditionswithyourteams.Itispossiblethatstudentswillhavefamilymembers,friendsorclassmateswithoneoftheseconditions.Itwouldbebeneficialtoexplaintoyourstudentsthatmanyfamiliescarrygeneticlinkstodifferentdiseases.Thereisagreatdealofresearchbeingdoneonthetreatmentanddetectionofgeneticdiseases.Manyconditionscanbetreatedand/ormanagedandindividualswiththeseconditionscanlivehappyproductivelives.
B. Pleaseconsultthechartbelowforinformationonthe6listedgeneticconditions.Frequenciesareapproximateandoftengivenforspecificgroups.Teamswillnotbeexpectedtoprovideanyofthisdetailedinformationbutshouldbeabletoidentifythegeneticconditionifgiventhespecificdetailsofthedisease.
GeneticCondition Descriptionof
Disease/ConditionFrequencyintheSpecificUSPopulation
GeneticDefect(mostcommon)/PatternofInheritance
CysticFibrosis Thebodyproducesstickymucusthatresultsinrespiratoryanddigestiveproblems
1/2500CaucasianAmericans
MutationsintheCFTRgene(autosomalrecessive)
SickleCellDisease Redbloodcellsbecomestiff,pileup,andcauseblockagesinsmallbloodvesselsandorgans
1/500AfricanAmericans Mutationinthehemoglobin-Betagene(autosomalrecessive)
Huntington’sdisease Progressivebraindisorderthatcausesuncontrolledmovements,emotionalproblemsandlossofthinkingability
1/10,000Americans Mutationinthehuntingtingene(autosomaldominant)
DownSyndrome Intellectualdisability,characteristicfacialappearanceandavarietyofbirthdefects
1/800births Trisomy21/errorinmeiosis
TurnersSyndrome Thesefemalesareusuallyshortinstature,mayhavewebbedneckandareinfertile
1/2,500females MonosomyX/errorinmeiosis
HemophiliaA(5thgradeonly)
Bleedingdisorderthataffectsthebloodsabilitytoclot
1/5000males MutationintheFactorVIIIgene(Xlinkedrecessive)
https://www.genome.gov/10001204/http://positivemed.com/2014/03/24/10-common-genetic-disorders/https://ghr.nlm.nih.gov/condition
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GlossaryofTermsDNA(deoxyribonucleicacid)Themoleculethatcarriesthegeneticinstructionsfoundinhumancellsandmostotherformsoflifeonearth.RNA(ribonucleicacid)Themoleculethatisgeneratedduringtranscriptionandplaysanessentialroleinproteinsynthesis.ThestructureissimilartoDNA.NucleotideThebuildingblockofDNAandRNA.Itiscomprisedofaphosphate,asugarandabase;adenine(A),thymine(T),cytosine(C)orguanine(G).InRNA,uracil(U)isusedinsteadofthymine.MutationAchangeintheDNAsequencethatmakesupagene,suchthatthesequencediffersfromwhatiscommonlyfound.Mutationscanbegood,badorjustdifferentversionsofthatgene.CodonAsequenceofthreenucleotidesinagenethatcorrespondstoaspecificaminoacidorastopsignalduringproteinproduction.CodonsprovidethecodethatallowsaDNAsequencetobetranslatedintoaproteinsequence.TranscriptionThetransferofaDNAsequenceintoRNA.TranslationTheprocessinwhichthegeneticcodecarriedbyRNAdirectsthesynthesisofproteinsfromaminoacids.CodingStrandThe5’to3’sequenceofagenethatcontainsthegeneticcodefortheaminoacidsequenceofaprotein.TemplateStrandThe3’to5’sequenceofagenethatisusedduringtranscriptionasatemplateforRNAproduction.ChromosomeAtightlypackedindividualmoleculeofDNAlocatedinthenucleus.Humanshaveatotalof46chromosomes,23pairs.HomologousChromosomesThetwochromosomepairofanyindividualchromosometype.Oneisinheritedfromthemother,andonefromthefather.CentromereAspecializedchromosomeregiontowhichspindlefibersattachduringcelldivision.GBandingAtechniquewhereGiemsastainisusedtocreateaspecificbandingpatternoneachchromosomesothattheycanbeidentifiedandanalyzedforabnormalities.AcrocentricAchromosomewiththecentromerelocatednearoneend.MetacentricAchromosomewiththecentromerelocatedinthecenter.
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SubmetacentricAchromosomewiththecentromerelocatedbetweenthecenterandtheend.KaryotypeThenumber,sizeandshapeofanindividual’schromosomes.Anindividual’skaryotypeisoftendisplayedasakaryogram,whichisaphotographoftheindividual’sstainedchromosomesKaryogramTheactualdisplayofasetofchromosomes.MonosomyWhenanindividualismissingachromosome.TrisomyWhenanindividualhasanextrachromosome.MitosisWhenonecelldividesinto2geneticallyidenticaldaughtercells.MeiosisTworoundsofcelldivisionresultingin4cellswithhalfthenumberofchromosomesoftheoriginalstartingcell.TraitPhysicalorbehavioralcharacteristics.Traitscanbeinheritedoracquired.HeredityThepassingoftraitsfromparentstooffspringthroughtheinheritanceofgenes.GeneThesegmentofDNAthatcontainsthespecificinstructionsformakingaprotein.AlleleDifferentversionofagene,DNAsequencewilldiffer.HomozygousHavingthesametwoversionsofanallele.HeterozygousHavingdifferentversionsofanallele.DominantThealleleforatraitthatwilldetermineanindividual’sphenotypewhentheyareheterozygous.Theallelethatisexpressed.RecessiveThealleleforatraitthathasnoeffectonphenotypewhenpresentinaheterozygousindividual.Itisonlyexpressedwhenyouhavetwocopiesofthisallele.X-LinkedRecessiveGenecarriedontheXchromosomethatisrecessiveinfemalesbutactsinadominatefashioninmalesbecauseonlyonecopyispresentPhenotypeAnorganism’sphysicalorexpressedtraits.Whattheylooklike.GenotypeTheallelesanorganismhas.Theirgeneticmake-up.PedigreeChartAdiagramusingsymbolsandlinestorepresentpeopleandrelationshipsmakingiteasiertovisualizetherelationshipswithinfamilies.Itrecordstheappearanceofaparticularphenotypeforagenewithinthefamily.PunnettSquareAgraphicalwaytosetupahypotheticalcrossorbreedingbetweentwoparentsanddetermineallthepossiblegeneticcombinationsorgenotypesoftheoffspring.
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AdditionalResourceshttps://www.soinc.org/heredity_bhttp://www.nclark.net/Geneticshttp://peer.tamu.edu/NSF_Files/Introduction%20to%20Genetics.ppthttp://knowgenetics.orghttp://www.sciencekidsathome.com/science_topics/genetics-a.htmlhttps://kidsbiology.com/biology-basics/the-science-of-genetics/
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AppendixA
IdentifywhatpartoftheDNAmoleculeeachletterrepresents. A ___________________________ B ___________________________ C ___________________________ D ___________________________ E ___________________________ F ___________________________ G ___________________________ H ___________________________ I ___________________________ adenine,cytosine,thymine,guanine,doublehelix,phosphate,deoxyribosesugar,5’ end,3’end
A
B
C D
E
F G
H
I
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AppendixB
GENE-iusDNACodonTable
(DNAnucleotidetripletstoaminoacids)2ndbase
1stbase T C A G 3rdbase
TTTT-Phenylalanine TCT-Serine TAT-Tyrosine TGT-Cysteine T
CAG
TTC-Phenylalanine TCC-Serine TAC-Tyrosine TGC-CysteineTTA-Leucine TCA-Serine TAA-Stop TGA-StopTTG-Leucine TCG-Serine TAG-Stop TGG-Tryptophan
C
CTT-Leucine CCT-Proline CAT-Histidine CGT-Arginine TCAG
CTC-Leucine CCC-Proline CAC-Histidine CGC-ArginineCTA-Leucine CCA-Proline CAA-Glutamine CGA-ArginineCTG-Leucine CCG-Proline CAG-Glutamine CGG-Arginine
A
ATT-Isoleucine ACT-Threonine AAT-Asparagine AGT-Serine TCAG
ATC-Isoleucine ACC-Threonine AAC-Asparagine AGC-SerineATA-Isoleucine ACA-Threonine AAA-Lysine AGA-ArginineATG–Methionine(start) ACG-Threonine AAG-Lysine AGG-Arginine
G
GTT-Valine GCT-Alanine GAT–AsparticAcid GGT-Glycine TCAG
GTC-Valine GCC-Alanine GAC–AsparticAcid GGC-GlycineGTA-Valine GCA-Alanine GAA–GlutamicAcid GGA-GlycineGTG-Valine GCG-Alanine GAG–GlutamicAcid GGG-Glycine
Genesequence:ATGGTTCACAGTTTCTCGGGCAAATAG Aminoacidsequenceofprotein:Methionine-Valine-Histidine-Serine- Phenylalanine-Serine-Glycine-Lysine-stop IfgivenaDNAsequencenotstartingwithATG,theyshouldbeabletofind thefirstATGandstartreadingthetripletcodonsfromthatpoint. Genesequence:GACTAATGGGATATCCAACTCTTCGTGTATGA Aminoacidsequenceofprotein:Methionine-Glycine-Tyrosine-Proline- Threonine-Leucine-Arginine-Valine-stop Note:Sequencesgivenduringtheeventwillnotbecolorcodedasabove.5thgradeteamsmustalso beabletogiveanaminoacidsequenceifgivenaRNAsequence.
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AppendixC
Isthisindividualamaleorfemale?Isthekaryotypenormal?Howmanychromosomesdoesthisindividualhave?Ifthekaryotypeisnotnormal,whatistheabnormality?
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AppendixD
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AppendixE
PunnettSquares
1. Firstyouneedtodeterminethegenotypeoftheparents.Sometimesthegenotypeisknownbasedonthephenotype(i.e.-iftheindividualexpressestherecessivetraitthentheyhavetobehomozygousforthatrecessiveallele).Otherwise,thegenotypeswillbespecificallygiven.
2. Nextyouneedtodrawasquarewith4boxeswithinit.3. Eachalleleforparent1isplacedontheleftsideofthesquareandeachalleleofparent
2isplacedonthetopasshown.(orderdoesnotmatter)4. Thepossiblegenotypesoftheoffspringarethendeterminedbycombiningtheallelesof
theparentsintothe4possibleoutcomes,oneineachbox.5. Usingthisinformationyoucandeterminethepercentageofoffspringyoushouldexpect
foreachgenotypeandresultingphenotype.6. Belowaretwosamplecrossesofmiceforthetraitofeyecolor.Blackeyesare
dominantoverredeyes.
ParentalGenotypes:
Parent1HomozygousDominant
blackeyesBB
Parent2HomozygousRecessive
redeyesbb
b b
B
B
These4squaresrepresentthe4possiblegenotypes.Eachoneis25%ofthetotaloffspring.
Bb
Bb Bb
Bb
PossibleGenotypesand%:Bb,100%PossiblePhenotypeand%:blackeyes,100%
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ParentalGenotypes:
Parent1Heterozygousblackeyes
Bb
Parent2HomozygousRecessive
redeyesbb
b b
B
b These4squaresrepresentthe4possiblegenotypes.Eachoneis25%ofthetotaloffspring.
bb
Bb Bb
bb
PossibleGenotypesand%:Bb,50%bb,50%PossiblePhenotypeand%:blackeyes,50%redeyes,50%
SampleQuestionInpeaplants,seedtexturecomesintwotypes,roundorwrinkled.Theroundseedallele(R)isdominantoverthewrinkledseedallele(r).Twopeaplantsthatareheterozygousforseedtexturearecrossed.Answerthefollowingquestions.
Whatisthegenotypeofthetwoplantsusedinthiscross?___________________Whatisthephenotypeoftheseplants(roundseedsorwrinkledseeds)?_________________FilloutthePunnettsquarebelow.
Belowarefourpossiblegenotypes.Whatpercentageofeachgenotypewouldyouexpecttoseeintheoffspringofthiscross?Genotypes: RR Rr rrPercentages:_______% _______% _________%
Belowarethetwopossiblephenotypesforseedtexture.Whatpercentageofeachphenotypewouldyouexpecttoseeintheoffspringofthiscross?Phenotypes: round wrinkledPercentages:_______% _______%
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AppendixFPedigreeCharts
AutosomalDominantorRecessiveInheritancePatternsTryingtoidentifyatraitasdominantorrecessivecanbealittletrickyespeciallywhencarriersarenotidentified.Theeasiestwaytodothisistoruleoutadominanttrait.Ifatraitisdominant,thentheaffectedindividualwillhaveinheritedthatallelefromaparentandwillhaveanaffectedparent.
Thepedigreeontheleftcouldstillbearecessivetraitwiththefatherbeinghomozygousrecessiveandthemotherbeingheterozygous(carrier).Inordertodeterminethat,moreinformationintheformofmorefamilymemberswouldbeneeded.Herearethebasicguidelines:DominantInheritance
• Traitshouldnotskipgenerations.• Anaffectedpersonmarriedtoa"normal"personshouldhaveapproximately50%oftheoffspring
beingaffected.(Alsoindicatesthattheaffectedindividualisheterozygous).RecessiveInheritance
• Traitoftenskipsgenerations.• Ifbothoftheparentsareaffected,allofthechildrenshouldbeaffected.• Mostaffectedindividualshave"normal"parents.
Squaresareusedtoindicatemales.
Circlesareusedtoindicatefemales.
Individualsthatare“affected”orhavethetraitthatyouarestudyingareshaded.
Sometimes,ashapewillbehalfshadedifthatindividualisaknownheterozygousor“carrier”ofthattrait.Note–mostofthetimecarriersarenotidentified.
Alinebetweenamaleandfemaleindicatesamarriage.Alinedrawndownfromamarriagelineindicateschildren.Eachrowofindividualsrepresentsageneration.
MightbedominantCan’tbedominant.Mustberecessive
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• Whena"normal"personismarriedtoanaffectedindividual,allofthechildrenarenormal(indicatingthenormalparentishomozygousdominant).
• Ifa"normal"personismarriedtoanaffectedindividualandoneormoreofthechildrenisaffected,thenapproximatelyhalfofthechildrenshouldbeaffected.(Showingthatthe"normal"parentisheterozygous).
XLinkedRecessiveInheritancePatterns(5thgradeonly)● Traitismuchmorefrequentinmales.● Thereisnofathertosontransmissionofthetrait.Ifthereis,itexcludesXlinkedinheritance.● Thediseasecanskipgenerationswithcarrierfemales.
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SampleQuestionExaminethepedigreechartbelowforaconditioncalledFalconianemia(Forf).Eachnumberinthechartreferstotheindividualaboveit.Answerthequestionsbelow.
1. Isindividual#1maleorfemale?
2. Whatistherelationshipbetweenindividuals#5and#6?
3. Whatistherelationshipbetweenindividuals#3,#4,and#5?
4. Whatistherelationshipbetweenindividuals#1and#3?
5. Howmanygenerationsarerepresentedinthischart?
6. Whichindividualsrepresentaffectedindividuals(thosewithFalconianemia)?
7. Whatisthegenotypeofindividual#2?
8. DoyouthinkFalconianemiaisanautosomaldominantorrecessivetrait?
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AppendixG
HumanABOBloodTypes
SampleQuestionIfamanwhoisbloodtypeABmarriesawomanwhoisbloodtypeO,whatarethepossiblebloodtypesoftheirchildren?