The Basis of Heredity “Chapter 18” 1 Curriculum Outcomes 2 Key Terms 3 4 Questions Questions 1-3 page 596 5 Genes and Heredity •Can you identify members of a family by physical traits? Heredity – is the transmission of biological traits from •parent to offspring. •Genetics – Study of inheritance of biological traits. Biological traits are determined by genes, which are •specific segments of DNA. Humans are able to use this information to their •advantage. •Cows and Dogs produced •Crop plants 6 Activity 7 MendelelianMendelelian GeneticsGenetics 8 GregorGregor MendelMendel (1822(1822--1884)1884) ResponsibleResponsible forfor thethe LawsLaws governinggoverning InheritanceInheritance ofof TraitsTraits 9 GregorGregor JohannJohann MendelMendel AustrianAustrian monkmonk StudiedStudied thethe inheritanceinheritance ofof traitstraits inin peapea plantsplants DevelopedDeveloped thethe lawslaws ofof inheritanceinheritance Mendel'sMendel's workwork waswas notnot recognizedrecognized untiluntil thethe turnturn ofof thethe 20th20th centurycentury 10 GregorGregor JohannJohann MendelMendel BetweenBetween 18561856 andand 18631863,, MendelMendel cultivatedcultivated andand testedtested somesome 28,00028,000 peapea plantsplants HeHe foundfound thatthat thethe plants'plants' offspringoffspring retainedretained traitstraits ofof thethe parentsparents CalledCalled thethe ““FatherFather ofof GeneticsGenetics"" 11 SiteSite ofof GregorGregor MendelMendel’’ss experimentalexperimental gardengarden inin thethe CzechCzech RepublicRepublic 12 ParticulateParticulate InheritanceInheritance MendelMendel statedstated thatthat physicalphysical traitstraits areare inheritedinherited asas ““particlesparticles”” MendelMendel diddid notnot knowknow thatthat thethe ““particlesparticles”” werewere actuallyactually ChromosomesChromosomes && DNADNA 13 Gregor Mendel – Pioneer of Genetics Mendel tracked and recorded the transmission •of seven visible traits through several generations of the garden pea. To Keep track he called the first parents P and than Filial General F1 and so on. •Why did he work with a garden pea? •Garden peas have a number of Characteristics How it reproduces- reproduces through self •pollination. 14 Seven Characteristics Studied By Mendel 15 The Principle of Dominance When Mendel used pollen from a pea plant with round •seeds to fertilize a pea plant with wrinkled seeds, he found that all the offspring (progeny) in the F1 generation had round seeds. Progeny – new individual that result from reproduction; •offspring. •Did this mean that pollen determines shape? So, he did the opposite and again all the progeny had •round seeds. Round-seed shape was always the dominant trait. •Mendel called the other wrinkled shaped seeds the recessive trait. 16 Questions Questions 1-5 page 600 17 GeneticGenetic TerminologyTerminology TraitTrait -- anyany characteristiccharacteristic thatthat cancan bebe passedpassed fromfrom parentparent toto offspringoffspring HeredityHeredity -- passingpassing ofof traitstraits fromfrom parentparent toto offspringoffspring GeneticsGenetics -- studystudy ofof heredityheredity 18 TypesTypes ofof GeneticGenetic CrossesCrosses MonohybridMonohybrid crosscross -- crosscross involvinginvolving aa singlesingle traittrait e.g.e.g. flowerflower colorcolor DihybridDihybrid crosscross -- crosscross involvinginvolving twotwo traitstraits e.g.e.g. flowerflower colorcolor && plantplant heightheight 19 PunnettPunnett SquareSquare UsedUsed toto helphelp solvesolve geneticsgenetics problemsproblems 20 21 DesignerDesigner ““GenesGenes”” AllelesAlleles -- twotwo formsforms ofof aa genegene (dominant(dominant && recessive)recessive) DominantDominant -- strongerstronger ofof twotwo genesgenes expressedexpressed inin thethe hybrid;hybrid; representedrepresented byby aa capitalcapital letterletter (R)(R) RecessiveRecessive -- genegene thatthat showsshows upup lessless oftenoften inin aa cross;cross; representedrepresented byby aa lowercaselowercase letterletter (r)(r) 22 MoreMore TerminologyTerminology GenotypeGenotype -- genegene combinationcombination forfor aa traittrait (e.g.(e.g. RR,RR, Rr,Rr, rrrr)) PhenotypePhenotype -- thethe physicalphysical featurefeature resultingresulting fromfrom aa genotypegenotype (e.g.(e.g. red,red, white)white) Segregation –the separation of alleles during meiosis 23 GenotypeGenotype && PhenotypePhenotype inin FlowersFlowers GenotypeGenotype ofof alleles:alleles: RR == redred flowerflower rr == yellowyellow flowerflower AllAll genesgenes occuroccur inin pairs,pairs, soso 22 allelesalleles affectaffect aa characteristiccharacteristic PossiblePossible combinationscombinations are:are: GenotypesGenotypes RRRR RRrr rrrr PhenotypesPhenotypes REDRED REDRED YELLOWYELLOW 24 GenotypesGenotypes HomozygousHomozygous genotypegenotype -- genegene combinationcombination involvinginvolving 22 dominantdominant oror 22 recessiverecessive genesgenes (e.g.(e.g. RRRR oror rrrr);); alsoalso calledcalled purepure HeterozygousHeterozygous genotypegenotype -- genegene combinationcombination ofof oneone dominantdominant && oneone recessiverecessive alleleallele ((e.g.e.g. Rr);Rr); alsoalso calledcalled hybridhybrid 25 Result of Peas being Crossed 26 Probability and Inheritance of Single Traits •Phenotypic ratio – the ratio of offspring with a dominant trait to the alternative recessive trait •Punnett Square – a chart used to determine the predicted outcome of a genetic cross. •Genotypic ratio – the ratio of offspring with each possible allele combination from a particular cross. •P = # of ways that a given outcome can occur Total # of possible outcomes 27 28 29 30 Review Questions •Page 475 Questions 1-4 (old text) •Questions 1-3 page 604 31 GenesGenes andand EnvironmentEnvironment DetermineDetermine CharacteristicsCharacteristics 32 MendelMendel’’ss PeaPea PlantPlant ExperimentsExperiments 33 WhyWhy peas,peas, PisumPisum sativumsativum?? CanCan bebe growngrown inin aa smallsmall areaarea ProduceProduce lotslots ofof offspringoffspring ProduceProduce purepure plantsplants whenwhen allowedallowed toto selfself--pollinatepollinate severalseveral generationsgenerations CanCan bebe artificiallyartificially crosscross--pollinatedpollinated 34 ReproductionReproduction inin FloweringFlowering PlantsPlants PollenPollen containscontains spermsperm ProducedProduced byby thethe stamenstamen OvaryOvary containscontains eggseggs FoundFound insideinside thethe flowerflower PollenPollen carriescarries spermsperm toto thethe eggseggs forfor fertilizationfertilization SelfSelf--fertilizationfertilization cancan occuroccur inin thethe samesame flowerflower CrossCross--fertilizationfertilization cancan occuroccur betweenbetween flowersflowers 35 MendelMendel’’ss ExperimentalExperimental MethodsMethods MendelMendel handhand--pollinatedpollinated flowersflowers usingusing aa paintbrushpaintbrush HeHe couldcould snipsnip thethe stamensstamens toto preventprevent selfself--pollinationpollination HeHe tracedtraced traitstraits throughthrough thethe severalseveral generationsgenerations 36 HowHow MendelMendel BeganBegan MendelMendel producedproduced purepure strainsstrains byby allowingallowing thethe plantsplants toto selfself-- pollinatepollinate forfor severalseveral generationsgenerations 37 EightEight PeaPea PlantPlant TraitsTraits SeedSeed shapeshape ------ RoundRound (R)(R) oror WrinkledWrinkled (r)(r) SeedSeed ColorColor -------- YellowYellow (Y)(Y) oror GreenGreen (y)(y) PodPod ShapeShape ------ SmoothSmooth (S)(S) oror wrinkledwrinkled (s)(s) PodPod ColorColor ------ GreenGreen (G)(G) oror YellowYellow (g)(g) SeedSeed CoatCoat ColorColor ------GrayGray (G)(G) oror WhiteWhite (g)(g) FlowerFlower positionposition------AxialAxial (A)(A) oror TerminalTerminal (a)(a) PlantPlant HeightHeight ------ TallTall (T)(T) oror ShortShort (t)(t) FlowerFlower colorcolor ------ PurplePurple (P)(P) oror whitewhite (p)(p) 38 39 40 MendelMendel’’ss ExperimentalExperimental ResultsResults 41 DidDid thethe observedobserved ratioratio matchmatch thethe theoreticaltheoretical ratio?ratio? TheThe theoreticaltheoretical oror expectedexpected ratioratio ofof plantsplants producingproducing roundround oror wrinkledwrinkled seedsseeds isis 33 roundround :1:1 wrinkledwrinkled MendelMendel’’ss observedobserved ratioratio waswas 2.96:12.96:1 TheThe discrepancydiscrepancy isis duedue toto statisticalstatistical errorerror TheThe largerlarger thethe samplesample thethe moremore nearlynearly thethe resultsresults approximateapproximate toto thethe theoreticaltheoretical ratioratio 42 GenerationGeneration ““GapGap”” ParentalParental PP1 GenerationGeneration == thethe parentalparental generationgeneration inin aa breedingbreeding experimentexperiment.. FF1 generationgeneration == thethe firstfirst--generationgeneration offspringoffspring inin aa breedingbreeding experiment.experiment. (1st(1st filialfilial generation)generation) FromFrom breedingbreeding individualsindividuals fromfrom thethe PP1 generationgeneration FF2 generationgeneration == thethe secondsecond--generationgeneration offspringoffspring inin aa breedingbreeding experiment.experiment. (2nd(2nd filialfilial generation)generation) FromFrom breedingbreeding individualsindividuals fromfrom thethe FF1 generationgeneration 43 FollowingFollowing thethe GenerationsGenerations CrossCross 22 ResultsResults CrossCross 22 HybridsHybrids PurePure inin allall getget PlantsPlants HybridsHybrids 33 TallTall && 11 ShortShort TTTT xx tttt TtTt TT,TT, TtTt,, tttt 44 MonohybridMonohybrid CrossesCrosses 45 PP11 MonohybridMonohybrid