solutions to genetics problems - bio 111 and 112 …

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1、SolutionstoGeneticsProblemsThischapterismuchmorethanasolutionsetforthegeneticsproblems.Hereyouwillfinddetailsconcerningtheassumptionsmade,theapproachestaken,thepredictionsthatarereasonable,andstrategiesthatyoucanusetosolveanygeneticsproblem.Thevalueofthischapterdep

2、endsonyou.Ineverycase,beforeyoulookhere,youshouldstrugglewiththeproblem,designyourownapproach,andmakeyourownmistakes.Onlythenshouldyoulookatthesolutionsgivenhere.(1)PROBLEMSINVOLVINGONLYONEGENE(1.1)Onegene;twoalleles;simpledominance(1.1.1)a)GGGG.Aplanthomozygousfo

3、rtheGalleleiscrossedtoanotherplanthomozygousfortheGallele.EachparenthasonlytheGalleletogivetoitsoffspring,sothePunnettsquareusedtopredicttheoffspringwouldlooklikethis:GGGGGGGgreengreenGGGGGgreengreenThispredictsalloffspring(100%)willhavethegenotypeofGGandgreenflowe

4、rcoloristhedominanttrait,soallhavegreenflowers.Becausebothparentsproduceonlyonetypeofgamete,youcansimplifythePunnettsquareto:GGGGgreenb)gggg.Aplanthomozygousforthegalleleiscrossedtoanotherplanthomozygousforthegallele.Eachparenthasonlythegalleletogivetoitsoffspring

5、,sothePunnettsquareusedtopredicttheoffspringwouldlooklikethis:gggggggorgblueblueggggggggblueblueblueThispredictsalloffspring(100%)willhavethegenotypeofggandblueflowercolor.1of57c)Gggg.Aheterozygousplantiscrossedtoaplanthomozygousforthegallele.Theheterozygotewillpa

6、sseithertheGorgalleletoitsoffspring.Theotherparenthasonlythegalleletogive.ThePunnettsquareusedtopredicttheoffspringwouldlooklikethis:GggGgggorGggreenbluegGggggGggggreenbluegreenblueBecausegreenflowercolorisdominanttoblueflowercolor,theGgoffspringwillhavegreenflower

7、sbutthehomozygousggoffspringwillhaveblueflowers.Thus,youwouldexpect50%oftheoffspringtobeGg(greenflowers)and50%tobegg(blueflowers).d)GgGg.Twoheterozygousplantsarecrossed.ThePunnettsquareusedtopredicttheoffspringwouldlooklikethis:GgGGGGggreengreengGggggreenblueThisp

8、redicts25%GGoffspring,50%Ggoffspring,and25%ggoffspring,a1:2:1genotypicratio.However,becausetheGgheterozygotesareindistinguishablefromtheGGhomozyg