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.