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Traits•Genetics–studyofhowtraitsarepassedfromparenttooffspring•Traitsaredeterminedbythegenesonthechromosomes.AgeneisasegmentofDNAthatdeterminesatrait.•Chromosomescomeinhomologouspairs,thusgenescomeinpairs.Homologouspairs–matchinggenes–onefromfemaleparentandonefrommaleparent•Example:Humanshave46chromosomesor23pairs.Onesetfromdad–23inspermOnesetfrommom–23ineggGeneforeyecolor(blueeyes)Geneforeyecolor(browneyes)Homologouspairofchromosomes•OnepairofHomologousChromosomes:Alleles–differentgenes(possibilities)forthesametrait–ex:blueeyesorbrowneyesDominantandRecessiveGenes•Genethatpreventstheothergenefrom“showing”–dominant•GenethatdoesNOT“show”eventhoughitispresent–recessive•Symbol–Dominantgene–uppercaseletter–TRecessivegene–lowercaseletter–tDominantcolorRecessivecolorExample:StraightthumbisdominanttohitchhikerthumbT=straightthumbt=hitchhikersthumb(Alwaysusethesameletterforthesamealleles—NoS=straight,h=hitchhiker’s)Straightthumb=TTStraightthumb=TtHitchhikersthumb=tt*Musthave2recessiveallelesforarecessivetraitto“show”•Bothgenesofapairarethesame–homozygousorpurebredTT–homozygousdominanttt–homozygousrecessive•Onedominantandonerecessivegene–heterozygousorhybridTt–heterozygousBB–BlackBb–Blackw/whitegenebb–WhiteGenotypeandPhenotype•Combinationofgenesanorganismhas(actualgenemakeup)–genotypeEx:TT,Tt,tt•Physicalappearanceresultingfromgenemake-up–phenotypeEx:hitchhiker’sthumborstraightthumbWhitefur(b)PunnettSquareandProbability•Usedtopredictthepossiblegenemakeupofoffspring–PunnettSquare•Example:Blackfur(B)isdominanttowhitefur(b)inmice1.Crossaheterozygousmalewithahomozygousrecessivefemale.Blackfur(B)Whitefur(b)HeterozygousmaleWhitefur(b)HomozygousrecessivefemaleBbBbbbbbWritetheratiosinthefollowingorders:Genotypicratiohomozygous:heterozygous:homozygousdominantrecessivePhenotypicratiodominant:recessivebbbBPossibleoffspring–2NMalegametes-N(Onegeneinsperm)Femalegametes–N(Onegeneinegg)Male=BbXFemale=bbGenotypicratio=2Bb:2bb50%Bb:50%bbPhenotypicratio=2black:2white50%black:50%whiteBBBbBbbbBbBGenotypicratio=1BB:2Bb:1bb25%BB:50%Bb:25%bbPhenotypicratio=3black:1white75%black:25%whiteCross2hybridmiceandgivethegenotypicratioandphenotypicratio.BbXBbbBBBbBbbbBbBbExample:Amanandwoman,bothwithbrowneyes(B)marryandhaveablueeyed(b)child.Whatarethegenotypesoftheman,womanandchild?BbXBbMan=BbWoman=Bb1brownandcurlyBBHHBBHhBbHHBbHhBBHhBBhhBbHhBbhhBbHHBbHhbbHHbbHhBbHhBbhhbbHhbbhhBHBHBhBhbHbHbhbh9blackandstraight3blackandcurly3brownandstraightGametesCrossinginvolving2traits–Dihybridcrosses•Example:Inrabbitsblackcoat(B)isdominantoverbrown(b)andstraighthair(H)isdominanttocurly(h).Cross2hybridrabbitsandgivethephenotypicratioforthefirstgenerationofoffspring.Possiblegametes:BbHhXBbHhBHBHBhBhbHbHbhbhPhenotypes-9:3:3:1BBHHBBHhGametesGametesBHBHBh100%blackandstraight•Example:Inrabbitsblackcoat(B)isdominantoverbrown(b)andstraighthair(H)isdominanttocurly(h).Crossarabbitthatishomozygousdominantforbothtraitswitharabbitthatishomozygousdominantforblackcoatandheterozygousforstraighthair.Thengivethephenotypicratioforthefirstgenerationofoffspring.BBHHXBBHhPossiblegametes:BHBHBh(Hint:OnlydesignPunnettsquarestosuitthenumberofpossiblegametes.)Phenotypes:SexDetermination•People–46chromosomesor23pairs•22pairsarehomologous(lookalike)–calledautosomes–determinebodytraits1pairisthesexchromosomes–determinessex(maleorfemale)•Females–sexchromosomesarehomologous(lookalike)–labelXXMales–sexchromosomesaredifferent–labelXYXXXXXYXYXY•Whatistheprobabilityofacouplehavingaboy?Oragirl?Chanceofhavingfemalebaby?50%malebaby?50%Whodeterminesthesexofthechild?fatherXXIncompletedominanceandCodominance•WhenonealleleisNOTcompletelydominantoveranother(theyblend)–incompletedominanceExample:Incarnationsthecolorred(R)isincompletelydominantoverwhite(W).Thehybridcolorispink.Givethegenotypicandphenotypicratiofromacrossbetween2pinkflowers.RWXRWRRRWR=1RR:2RW:1WWPhenotypic=1red:2pink:1white•Whenbothallelesareexpressed–CodominanceExample:Incertainchickensblackfeathersarecodominantwithwhitefeathers.Heterozygouschickenshaveblackandwhitespeckledfeathers.Sex–linkedTraits•GenesforthesetraitsarelocatedonlyontheXchromosome(NOTontheYchromosome)•XlinkedallelesalwaysshowupinmaleswhetherdominantorrecessivebecausemaleshaveonlyoneXchromosome•Examplesofrecessivesex-linkeddisorders:1.colorblindness–inabilitytodistinguishbetweencertaincolorsColorblindnessistheinabilitytodistinguishthedifferencesbetweencertaincolors.Themostcommontypeisred-greencolorblindness,whereredandgreenareseenasthesamecolor.Youshouldsee58(upperleft),18(upperright),E(lowerleft)and17(lowerright).2.hemophilia–bloodwon’tclotXNXNXNXnXNYXnYXNXnXNYPhenotype:2normalvisionfemales1normalvisionmale1colorblindmale•Example:Afemalethathasnormalvisionbutisacarrierforcolorblindnessmarriesamalewithnormalvision.Givetheexpectedphenotypesoftheirchildren.N=normalvisionn=colorblindnessXNXnXXNYPedigrees•Graphicrepresentationofhowatraitispassedfromparentstooffspring•Tipsformakingapedigree1.Circlesareforfemales2.Squaresareformales3.Horizontallinesconnectingamalean