Practice the genetic problems!!! Gamete formation was in the last lab… it is important to be able to set up punnett squares. At first we will assume that genes are inherited independently. In reality, chromosomes are inherited independently but often genes are on the same chromosome, and are thus linked. Mom ♀ (Bb) Eye Color Brown Eyes Dad ♂ (bb) Blue Eyes B B b Bb Bb b Bb bb Take notice; gametes were formed for the one contribution from mother and one from the father. Mother is on the top of the square since eggs are usually met by sperm. Much in the same way, a line graph has the changing factor on the side, minor detail but important. Gametes combine during recombination, fertilization, and one gene of each allele is combined. If you are keeping up from the previous week, this is the establishment of the diploid state, 2n. Dominant alleles are capital, recessive alleles are lowercase and each letter represents a gene. You have two copies of every gene, one maternal and one paternal. Dominant expresses over recessive. Homozygous has both of the same type of allele so homozygous dominant or homozygous recessive. Heterozygous has one of each copy, but appears as the dominant phenotype. The phenotype is the expressed trait… in the example, eye color. So that is the basics. But there are sex linked traits. So there isn’t a whole lot of info on the y chromosome; sorry guys! Since the sex of an individual will matter for sex linked crosses, always write X with a superscript of the gene, X+ as an example. There are also lethal alleles, usually recessive, so if an individual doesn’t have the other allele to compensate, you will never see them. Draw the punnet square and cross out those individuals that would die in utero. Incomplete dominance is when the heterozygous individual is a mix between the two extremes, think red + white = pink. Codominance is when both alleles are expressed together, think about blood types. Unfortunately blood type is a tricky one. Since O is recessive to both B and A we write it as i. IB and IA are the ways to write B and A copies. So you know the genotype of O and AB individuals but A and B individuals may be homozygous or have one i gene. Please also practice making gametes. You have 2 copies of each gene but only pass off one to your children, think meiosis! So again AaBBCCDD can possibly be ABCD or aBCD. Review the examples and read the lab beforehand, it helps immensely and shows. If you have questions still, come to office hours please. And remember the lab is due next week! GeneticsProblemsfor Practice In cats,the B allele codesfor black fur, andthe b allele codesfor yellow fur. The geneis locatedon the Xchromosome.However,the genotypeBb resultsin fur with a mottled appeaftmcecalledtortoise-shell.Suppose a tortoise-shellfemaleis crossedwith a black qale. mal What offspring would be expected?Would you expectany ,6 tortoise-shell males to be produced? Yb hr t, O I x B- btqcl( XB/ b X lellov^) x-vlxoy fit^cl 'lodooe I Blac! / fl Tello,o l,)uft'h''P g The allele "Au that enablesa personto tastethe chemicalPTC is dominantover the allele for the inability to tastePTC. In addition,recall that the allele for brown eyes(B) is dominantover the allele for blue eyes@). Supposetwo parents,eachwith the genotypeAaBb, havechildren. What proportionof thesechildrenwould be blue-eyedtasten of PTC?What proportionwould be blue-eyednon-tasters? A- l^slers ffib v 4 - r1Dyr-ht*'fs B - Brurn elPS ttueaf AB Ab oB ^b 3l /6 1,rt+dt A8 *h b'- trlueeles lgo i#r:l- ob pig that is homozygousrecessivehaswhite fur. 3. A dominantallele Tconfers blackfur on guineapigs. Fred would like to know whetherhis pet black-flrred guineapig is homozygousdominantor heterorygous. How might he useMendeliangeneticsto determinehis pet's genotype? I ;,) )A,sa c)orr,nqnlirrAil u dvJ &es/ cl^oss fti{' o_i$;-,.AR 3W w receg,le ' u u*'l * ")k^* t5 J5 *irffi,Lt\o "u,tive'n, "l Plantsthat breedtrue for tallnessandalso for red flowers are crossedwith shon white-floweredplants. The resultingF1generationconsistsentirely of tall pink-floweredplants.Assumingthe genesaxenot linked, predict the offspring that would be producedin the Fzgeneration. 1A {r +R t(fR, (r { ^ F,, 7TR,r 3 tuAGtt b P,rrK'trtll , t Qedthot{ A P,rt( 51Y.! IR all z wr,e ,^lh;l<.thNr iJI\(Y- iC t4.\ 5. In humans, normalskinpigmentation is dueto a dominantallele"A". Albinism(thelackof r[ir, tffi5Ltatilfi is dueto its recessiveallele "a". Supposea nomnl manwhosemotherwasalbino marriesa normal woman whosefatherwasalbino. What arethe chancesthat thev will havean albino child? A' no{nal qlbr /uo d ' #, q AAIM Aalaq Q{1, I U d. Blood typing hasbeenus,edas eridencein paterTry ( meanngfatherhood)cases,whenthe blood tlpe of the motherandchild may indicatethata manaitiea to be tne ruiirr.ouia.rot possiblehavefathered the child. For the following motherand,cfritacombinations,lndicate which bloodgroup,ofpotentiarfatherswourdbe exonerated.Tharis' which broodtype(s)*ourd b" it p"rili;;;;idrr,", to have? Man exoneratedif he belongsto blood groups / b. O, 4 c.A d. AB e. B,O 7' supposethat geneb is sex-linked,recessiveand le1h4!-when it is marriesa womanwho is heterozygousfor this g";;Trth;;;fi;L"" not maskedby the dominantallele. A man manynormarchildren, what would be thepredictedsexratio ofthesecliiArenf XB Y, ;ur-f"'fro 8' ag:1,/ x3 AII the offspring glodugedby crossing.red-flowered plantswith white-floweredplantshavepink flowers. flower colors(and in whatpropottio;) would be ro*o in trr" offspring i" Jitrrc following crosses: "".r, RR-rnl,, 'o?'"0,- -"0',1.0': fffil !,'::LlM ( r l-Br lrr I l(n/Rr,l e' f,: HfiYJil:$H*t#if;""j*| nies, ageneticist d.j"ry'lg" Berween Aandc:rlo/o crossing-over berween genes occurred in Dsrwevu Between vcandD:4oo/o {ruur 3:,ffi:il1,ili3i3/in"," T p",+L"s l *'fl"ffi,?ruin;l*".. u""", s.rr#n$ irrYc,Yo"r" ? A qdA qrn'v'q*s "f 141,andsolidcolor(,f) is dominant ,9J l0' In cockroaches' blackcolor(B) is dominantto nro*n cockroach heterozygous for boththesehaitsy"r::.*tF :nXf"t#lT;J::::ffi:i fi-LlaeK i - -anwl, 7 ) ,.1 ilS S to spotted(s). A 4 uro*n, spottediochoach. rt eyprooucehundre4s of ratio istoutact< sorid :5ui".l-'p'ffii;ffiffi1 ,i!"il.f*,,spotted. How Lbss rJO'"rs Bbicxx "": n, t!: #: #s . t:2 Bs BB 8B qtr65 5s 1;3:3;t elrych)e.a gB 65 Yrett A t!;lr,tl,l,n, 8-sptt EB BbSs IJ],tt t BtSt_663s f LSa As Bb4 Abas\b4 [bag w l' A fruit fly having a geno0pe of ffis what is the genotypicratio of the many.resultingoffspring? ryd. Z L pe'rts n"kA h receJS'v FT { FreI 1{.C,'IC€ , \\ t \ I €tN In peaplants,the allele for tallnessis dominantover the allele for shortness.If you crossa plant that breedstrue for shorfiresswith a heterozygousplant, what percentage of the resurtingoifrpri.rj*o,itJi" tiE! "*p..r"a -r-:'qll f f 5cz +-5Aur4 + X gLorl A man andhis wife both havenormalcolor vision, but a daughterhasred-greencolorblindness,a sexIinkedrecessive trait. Themansueshis wife for divorpeoo fo*or ofinna"rity. can geneticsprovide evidencequpportinghis case? + t'- fiotrtral I I ... r mal? Y1e{ficll a X- _X' X-IX*y*lf.r-l x'x- ;^"'";r^',;;'-prolw( X ukbli; v Ca{fief le^o leE Xy Supposetwo genesarelinked, with genesw and zon onememberof a homologouspair of chromosomesand p andz on the othermember.tran inaivioual hasa g"notyp. oi iihr,what -sameteswould that individual produceifcrossing-overdid occurbetweenthose ivo g"i"ri 'rl v),th c fDsrtng ov((r l)ttlla7e il 5o I tl- WWLZ v l nelalel } Summer)qu4ru uuruusr squash4rc areerrnertilnlre eitherwhitetfyeltow. or yellow, To getw![e squash,at To get white. Theallelefor whichcororii oominantz"n*prffiyoi" rr*o, ;€ MalQ u)h;lL q yellods CaA receJl;,J4r two i5 , dh;lL V I b+h a{e Tellow't^, /- parcri{ aft DPPDiltq lo t: ;l't ltt *rh;# Jrh,'/ni5 donitta'rr 6. A womanwith type AB blood marriesa manhomozygousfor type A blood, what could be the possible blood typesof their children? ,t t2 TN -Lt T' TA l / A+ lB Tr^lT'f 7' All the offsRrine.qrodycedby crossingred-floweredplantswith white-floweredplantshavepink flowers. what flower colo(s) (and in what proportionslwould be found in the offspring ortr," rotio*iog cros.: pink x .n/'\ O /) | ;q(-ke"( .N rT 'a ,I r lUrlrr I Rr-P|nR r'r v)h;+L r tkQ\ , tfa ,/a ^ P;nK tDA,tz A womanis a carrier for-a sex'linkedgenethat causesan embryoto -- -'spontaneouslyabort. she hasnine children.How manyof thesectrilaren$VE expgct!oU. Uoyri- I"i': ti4nYa"!'J'3 a9:lD /'Y lnl { F-c* - aBer tke Supposethat-indragons,the ability to breathefire is dueto a dominant allele,andthe inability to breathe fire (smolderingonly) is dueto itsrecessiveallele. The dominant alleieof anothergeneis responsible for scaleson the dragon'sskin; its reces-sive allelegivesa scale-less .onaition. what genotypicand phenotypicratios would be expectedfrom a cro-ssbetween one smolderingscalelessdragonand one firebreathingdragonthat hasscales? l"l; / :l s,rolder,nl Khlcl ; - ro 10. Thepercentage of crossing-over l{ue aft [ (,,eL'lal is L,iluozY1 'lrrlo ryof€-,.' betweenfour linkedgenes(K, L,M &N) is asfollows: ....BerweenM andN: 8 % Betweenr *a l: ffi t;;;; M andL: 19 Yo BetweenKandN 5 % BetweenNandL:ll% What is the sequenceof geneson the chromosome? ,]- h 5 fthe *W95 tl Yl @KN ffiL Al b+hl: \