Genetics: A Crash Course
Transcript of Genetics: A Crash Course
Genetics: A Crash Course Terminology: Allele:Aspecificformofagene.Youcanhaveanalleleforblueeyesorgreeneyesforexample.Genotype:thespecificallelesofanorganism.(AS,Aa,etc.)(I,e.thegenes)Phenotype:theobservablecharacteristicsortraitsofanorganism.Dominantallele:anallelethathasthesameeffectonthephenotypewhetheritispresentinthehomozygousorheterozygousstate.Recessiveallele:anallelethatonlyhasaneffectonthephenotypewhenpresentinthehomozygousstate.Co-dominantalleles:pairsofallelesthatbothaffectthephenotypewhenpresentinaheterozygote.Homozygous:havingtwoidenticalallelesofagene.(RRorrr)Heterozygous:havingtwodifferentallelesofagene.(Rr) Mendel and the Basics:
o Animalsandplantsinheritonegenefromeachoftheirparents.o Thismeanseachindividualhastwocopiesofageneforasingletrait.Wecallthesecopies
alleles.o GregorMendel(1822-1884)wasanAustrianMonkwhostudiedpeaplants.Henoticedpatterns
intheinheritanceofpeaplantsashecrossbredthem.Pleaseanswerthetwoquestionsbelowfromthevideo:GregorMendel–Greatminds.
1) What traits did Mendel observe in the pea plants?
2) What three important conclusions did Mendel come to when crossing the true breeding white and purple pea flower lines?
Pea Colour and Mendel:
TwoAlleles–Y=Yellowpeas,y=Greenpeas.1.ThegenesforyellowpeasarerepresentedbyacapitalY.IfaplantgetsaYfromeachparent,thegenotypewouldbeYY. YY=YellowPeas2.Thegenesforgreenpeasarerepresentedbyalowercasey.Ifaplantgetsayfromeachparent,thegenotypewouldbeyy. yy=GreenPeas3.WhathappensifaplantgetsYfromoneparentandayfromanotherparent? Yy=YellowPeasThismeansthatYforyellowpeasisdominantsinceitonlyneedsonecopyforthattobe
expressed!Figuring out Inheritance Wecanuseapunnetsquaretofigureoutthepotentialinheritancefromtwoparents!Example:Whathappensifwecrosstwoheterozygousyellowparents?YyxYy?Whatarethepossibleoutcomesfortheparents?
Practice:GetarandomgenotypefromMr.Pletsch.Findthreedifferentpartnersandbreedyourpeaplantsforpeacolourandcompleteapunnetsquare.Remember:YY=Yellow,Yy=Yellow,yy=GreensinceYellow(Y)isdominant!
Genetics: Inheritance of Blood Types
o Sofar,wehaveonlybeenconsideringtwopossibilities:dominantAandrecessivea.o Twoalleles(dom/rec)–threegenotypespossible(AA,Aa,aa)andtwophenotypes.
o However,inrealitytherecanbethreeormoreallelesforonegene.HumanBloodTypeshavemultiplealleles–A,B,O!Thismakesourpunnetsquaresabitmoredifficultsincetherearemoreoutcomes.WithMendel’speas–wecouldhaveYY,Yy,yy.Withbloodtypes–wecouldhaveAA,AO,BB,BO,AB,OO!Anotherthingtoconsider–bloodtypesshowco-dominance!ThatbothAandBaredominantandbothallelesareexpressed!Forexample:
Mendel’sPeas–Regulardominant/recessive
HumanBloodTypes-Codominance
100%ofoffspringwillbeYy(YellowPeas) 100%ofOffspringwillbeABbloodtype–bothA
andBantigenswillbepresent!
NOTE:AandBarecodominantbutOisrecessive!Thisleadsto4bloodtypes
AA=BloodtypeAAO=BloodtypeABB=BloodTypeBBO=BloodTypeBAB=BloodTypeABOO=BloodTypeO
Practice:
1. Finishthepunnetsquaresbelow:
BloodTypesPossible:
BloodTypesPossible:
BloodTypesPossible:
BloodTypesPossible:
BloodTypesPossible:
BloodTypesPossible:
2. OneparenthasbloodtypeAwhiletheotherparenthasbloodtypeB.Theyhaveachildwith
BloodtypeO.Howisthispossible?Useapunnetsquaretohelpyouexplain.