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 ƒƒAustrianAustrian monkmonk ƒƒStudiedStudied thethe inheritanceinheritance ofof traitstraits inin peapea plantsplants ƒƒDevelopedDeveloped thethe lawslaws ofof inheritanceinheritance ƒƒMendel'sMendel's workwork waswas notnot recognizedrecognized untiluntil thethe turnturn ofof thethe 20th20th centurycentury

10 GregorGregor JohannJohann MendelMendel ƒƒBetweenBetween 18561856 andand 18631863,, MendelMendel cultivatedcultivated andand testedtested somesome 28,00028,000 peapea plantsplants ƒƒHeHe foundfound thatthat thethe plants'plants' offspringoffspring retainedretained traitstraits ofof thethe parentsparents ƒƒCalledCalled thethe ““FatherFather ofof GeneticsGenetics""

11 SiteSite ofof GregorGregor MendelMendel’’ss experimentalexperimental gardengarden inin thethe CzechCzech RepublicRepublic

12 ParticulateParticulate InheritanceInheritance

ƒƒMendelMendel statedstated thatthat physicalphysical traitstraits areare inheritedinherited asas ““particlesparticles”” ƒƒMendelMendel 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 ƒƒ TraitTrait -- anyany characteristiccharacteristic thatthat cancan bebe passedpassed fromfrom parentparent toto offspringoffspring ƒƒ HeredityHeredity -- passingpassing ofof traitstraits fromfrom parentparent toto offspringoffspring ƒƒ GeneticsGenetics -- studystudy ofof heredityheredity

18 TypesTypes ofof GeneticGenetic CrossesCrosses

ƒƒ MonohybridMonohybrid crosscross -- crosscross involvinginvolving aa singlesingle traittrait e.g.e.g. flowerflower colorcolor ƒƒ 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”” ƒƒ AllelesAlleles -- twotwo formsforms ofof aa genegene (dominant(dominant && recessive)recessive) ƒƒ DominantDominant -- strongerstronger ofof twotwo genesgenes expressedexpressed inin thethe hybrid;hybrid; representedrepresented byby aa capitalcapital letterletter (R)(R) ƒƒ RecessiveRecessive -- genegene thatthat showsshows upup lessless oftenoften inin aa cross;cross; representedrepresented byby aa lowercaselowercase letterletter (r)(r)

22 MoreMore TerminologyTerminology

ƒƒ GenotypeGenotype -- genegene combinationcombination forfor aa traittrait (e.g.(e.g. RR,RR, Rr,Rr, rrrr)) ƒƒ PhenotypePhenotype -- thethe physicalphysical featurefeature resultingresulting fromfrom aa genotypegenotype (e.g.(e.g. red,red, white)white) ƒ 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 ƒƒ HomozygousHomozygous genotypegenotype -- genegene combinationcombination involvinginvolving 22 dominantdominant oror 22 recessiverecessive genesgenes (e.g.(e.g. RRRR oror rrrr);); alsoalso calledcalled purepure ƒƒ 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??

ƒƒCanCan bebe growngrown inin aa smallsmall areaarea ƒƒProduceProduce lotslots ofof offspringoffspring ƒƒProduceProduce purepure plantsplants whenwhen allowedallowed toto selfself--pollinatepollinate severalseveral generationsgenerations ƒƒCanCan 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 CrossCross Trait:Trait: SeedSeed ShapeShape Alleles:Alleles: RR –– RoundRound rr –– WrinkledWrinkled Cross:Cross: RoundRound seedsseeds xx WrinkledWrinkled seedsseeds RRRR xx rrrr

r r Genotype:Genotype: RrRr

PhenotypePhenotype: RoundRound

R Rr Rr GenotypicGenotypic Ratio:Ratio: AllAll alikealike

R Rr Rr PhenotypicPhenotypic Ratio:Ratio: AllAll alikealike

46 PP11 MonohybridMonohybrid CrossCross ReviewReview

ƒƒ HomozygousHomozygous dominantdominant xx HomozygousHomozygous recessiverecessive ƒƒ OffspringOffspring allall HeterozygousHeterozygous (hybrids)(hybrids)

ƒƒ OffspringOffspring calledcalled FF1 generationgeneration ƒƒ GenotypicGenotypic && PhenotypicPhenotypic ratioratio isis ALLALL ALIKEALIKE

47 FF11 MonohybridMonohybrid CrossCross Trait:Trait: SeedSeed ShapeShape Alleles:Alleles: RR –– RoundRound rr –– WrinkledWrinkled Cross:Cross: RoundRound seedsseeds xx RoundRound seedsseeds RrRr xx RrRr

R r Genotype:Genotype: RR,RR, Rr,Rr, rrrr

PhenotypePhenotype: RoundRound && R RR Rr wrinkledwrinkled G.Ratio:G.Ratio: 1:2:11:2:1

r Rr rr P.Ratio:P.Ratio: 3:13:1

48 FF11 MonohybridMonohybrid CrossCross ReviewReview

ƒƒ HeterozygousHeterozygous xx heterozygousheterozygous ƒƒ Offspring:Offspring: 25%25% HomozygousHomozygous dominantdominant RRRR 50%50% HeterozygousHeterozygous RrRr 25%25% HomozygousHomozygous RecessiveRecessive rrrr

ƒƒ OffspringOffspring calledcalled FF2 generationgeneration ƒƒ GenotypicGenotypic ratioratio isis 1:2:11:2:1 ƒƒ PhenotypicPhenotypic RatioRatio isis 3:13:1

49 WhatWhat DoDo thethe PeasPeas LookLook Like?Like?

50 ……AndAnd NowNow thethe TestTest CrossCross

MendelMendel thenthen crossedcrossed aa purepure && aa

hybridhybrid fromfrom hishis FF2 generationgeneration

ThisThis isis knownknown asas anan FF2 oror testtest crosscross ThereThere areare twotwo possiblepossible testcrosses:testcrosses: HomozygousHomozygous dominantdominant xx HybridHybrid HomozygousHomozygous recessiverecessive xx HybridHybrid

51 stst FF22 MonohybridMonohybrid CrossCross (1(1 )) Trait:Trait: SeedSeed ShapeShape Alleles:Alleles: RR –– RoundRound rr –– WrinkledWrinkled Cross:Cross: RoundRound seedsseeds xx RoundRound seedsseeds RRRR xx RrRr

R r Genotype:Genotype: RR,RR, RrRr

PhenotypePhenotype: RoundRound

R RR Rr GenotypicGenotypic Ratio:Ratio: 1:11:1

R RR Rr PhenotypicPhenotypic Ratio:Ratio: AllAll alikealike

52 FF22 MonohybridMonohybrid CrossCross (2nd)(2nd) Trait:Trait: SeedSeed ShapeShape Alleles:Alleles: RR –– RoundRound rr –– WrinkledWrinkled Cross:Cross: WrinkledWrinkled seedsseeds xx RoundRound seedsseeds rrrr xx RrRr

R r Genotype:Genotype: Rr,Rr, rrrr

PhenotypePhenotype: RoundRound && r Rr rr WrinkledWrinkled G.G. Ratio:Ratio: 1:11:1

r Rr rr P.Ratio:P.Ratio: 1:11:1

53 FF22 MonohybridMonohybrid CrossCross ReviewReview

ƒƒ HomozygousHomozygous xx heterozygous(hybrid)heterozygous(hybrid) ƒƒ Offspring:Offspring: 50%50% HomozygousHomozygous RRRR oror rrrr 50%50% HeterozygousHeterozygous RrRr ƒƒ PhenotypicPhenotypic RatioRatio isis 1:11:1 ƒƒ CalledCalled TestTest CrossCross becausebecause thethe offspringoffspring havehave SAMESAME genotypegenotype asas parentsparents

54 PracticePractice YourYour CrossesCrosses

WorkWork thethe PP11,, FF11,, andand bothboth

FF22 CrossesCrosses forfor eacheach ofof thethe otherother SevenSeven PeaPea PlantPlant TraitsTraits

55 MendelMendel’’ss LawsLaws

56 ResultsResults ofof MonohybridMonohybrid CrossesCrosses InheritableInheritable factorsfactors oror genesgenes areare responsibleresponsible forfor allall heritableheritable characteristicscharacteristics PhenotypePhenotype isis basedbased onon GenotypeGenotype EachEach traittrait isis basedbased onon twotwo genesgenes,, oneone fromfrom thethe mothermother andand thethe otherother fromfrom thethe fatherfather TrueTrue--breedingbreeding individualsindividuals areare homozygoushomozygous (( bothboth alleles)alleles) areare thethe samesame

57 LawLaw ofof DominanceDominance InIn aa crosscross ofof parentsparents thatthat areare purepure forfor contrastingcontrasting traitstraits,, onlyonly oneone formform ofof thethe traittrait willwill appearappear inin thethe nextnext generation.generation. AllAll thethe offspringoffspring willwill bebe heterozygousheterozygous andand expressexpress onlyonly thethe dominantdominant trait.trait. RRRR xx rrrr yieldsyields allall RrRr (round(round seeds)seeds)

58 LawLaw ofof DominanceDominance

59 LawLaw ofof SegregationSegregation

DuringDuring thethe formationformation ofof gametesgametes (eggs(eggs oror sperm),sperm), thethe twotwo allelesalleles responsibleresponsible forfor aa traittrait separateseparate fromfrom eacheach other.other. AllelesAlleles forfor aa traittrait areare thenthen "recombined""recombined" atat fertilizationfertilization,, producingproducing thethe genotypegenotype forfor thethe traitstraits ofof thethe offspringoffspring.

60 ApplyingApplying thethe LawLaw ofof SegregationSegregation

61 LawLaw ofof IndependentIndependent AssortmentAssortment

AllelesAlleles forfor differentdifferent traitstraits areare distributeddistributed toto sexsex cellscells (&(& offspring)offspring) independentlyindependently ofof oneone another.another. ThisThis lawlaw cancan bebe illustratedillustrated usingusing dihybriddihybrid crossescrosses..

62 DihybridDihybrid CrossCross AA breedingbreeding experimentexperiment thatthat trackstracks thethe inheritanceinheritance ofof twotwo traitstraits.. MendelMendel’’ss ““LawLaw ofof IndependentIndependent AssortmentAssortment”” a.a. EachEach pairpair ofof allelesalleles segregatessegregates independentlyindependently duringduring gametegamete formationformation b.b. Formula:Formula: 22n (n(n == ## ofof heterozygotes)heterozygotes)

63 Question:Question: HowHow manymany gametesgametes willwill bebe producedproduced forfor thethe followingfollowing alleleallele arrangements?arrangements?

Remember:Remember: 22n (n(n == ## ofof heterozygotes)heterozygotes)

1.1. RrYyRrYy

2.2. AaBbCCDdAaBbCCDd

3.3. MmNnOoPPQQRrssTtQqMmNnOoPPQQRrssTtQq

64 Answer:Answer: 1.1. RrYy:RrYy: 22n == 222 == 44 gametesgametes

RYRY RyRy rYrY ryry

2.2. AaBbCCDd:AaBbCCDd: 22n == 223 == 88 gametesgametes

ABCDABCD ABCdABCd AbCDAbCD AbCdAbCd aBCDaBCD aBCdaBCd abCDabCD abCDabCD

3.3. MmNnOoPPQQRrssTtQq:MmNnOoPPQQRrssTtQq: 22n == 226 == 6464 gametesgametes

65 DihybridDihybrid CrossCross Traits:Traits: SeedSeed shapeshape && SeedSeed colorcolor Alleles:Alleles: R round r wrinkled Y yellow y green RrYy x RrYy

RYRY RyRy rYrY ryry RYRY RyRy rYrY ryry

AllAll possiblepossible gametegamete combinationscombinations

66 DihybridDihybrid CrossCross

RY Ry rY ry

RY

Ry rY ry

67 DihybridDihybrid CrossCross

RY Ry rY ry

Round/Yellow: 9 RY RRYY RRYy RrYY RrYy

Round/green: 3 Ry RRYy RRyy RrYy Rryy

wrinkled/Yellow: 3 rY RrYY RrYy rrYY rrYy wrinkled/green: 1 ry RrYy Rryy rrYy rryy 9:3:3:1 phenotypic ratio

68 DihybridDihybrid CrossCross

Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1

69 Test Crosses Wool producers often prefer white wool, since •black wool is brittle and difficult to dye.

Black sheep can be avoided by breeding only •homozygous white rams. However the allele for white wool (W) is dominant over the allele for black wool (w), so white rams can be heterozygous. How can a woo producer be sure that a white ram is homozygous?

•Test Cross – the cross of an individual of unknown genotype to an individual that is fully recessive.

70 Test Cross

71 TestTest CrossCross AA matingmating betweenbetween anan individualindividual ofof unknownunknown genotypegenotype andand aa homozygoushomozygous recessiverecessive individual.individual. Example:Example: bbC__bbC__ xx bbccbbcc

BBBB == brownbrown eyeseyes BbBb == brownbrown eyeseyes bbbb == blueblue eyeseyes bC b___

bc CCCC == curlycurly hairhair CcCc == curlycurly hairhair cccc == straightstraight hairhair

72 TestTest CrossCross PossiblePossible results:results:

bC b___C bC b___c bc bbCc bbCc or bc bbCc bbcc

73 SummarySummary ofof MendelMendel’’ss lawslaws PARENT LAW OFFSPRING CROSS

DOMINANCE TT x tt 100% Tt tall x short tall

Tt x Tt 75% tall SEGREGATION tall x tall 25% short

9/16 round seeds & green RrGg x RrGg pods INDEPENDENT 3/16 round seeds & yellow round & green pods ASSORTMENT x 3/16 wrinkled seeds & green pods round & green 1/16 wrinkled seeds & yellow pods

74 IncompleteIncomplete DominanceDominance andand CodominanceCodominance

75 Incomplete Dominance •Incomplete dominance – the expression of both forms of an allele in heterozygous individual in cells of an organism, producing an intermediate phenotype.

76 Incomplete Dominance

77 IncompleteIncomplete DominanceDominance

F1F1 hybridshybrids have an appearance somewhat inin betweenbetween the phenotypesphenotypes of the two parental varieties. Example:Example: snapdragonssnapdragons (flower)(flower) red (RR) x white (rr) r r

RRRR == redred flowerflower R rr = white flower R

78 IncompleteIncomplete DominanceDominance

r rr producesproduces thethe RR RrRr RrRr FF1 generationgeneration

RR RrRr RrRr AllAll RrRr == pinkpink (heterozygous(heterozygous pink)pink)

79 IncompleteIncomplete DominanceDominance

80 Codominance •Codominance – the expression of both forms of an allele in heterozygous individual in different cells of the same organism

81 Codominance

82 CodominanceCodominance

TwoTwo allelesalleles areare expressedexpressed ((multiplemultiple allelesalleles)) inin heterozygousheterozygous individualsindividuals.. Example:Example: bloodblood typetype

1.1. typetype AA == IIAIIA oror IIAii 2.2. typetype BB == IIBIIB oror IIBii 3.3. typetype ABAB == IIAIIB 4.4. typetype OO == iiii

83 CodominanceCodominance ProblemProblem

Example: homozygous male Type B (IBIB) x heterozygous female Type A (IAi)

IA i

A B B B I I I i I 1/2 = IAIB 1/2 = IBi IB IAIB IBi

84 AnotherAnother CodominanceCodominance ProblemProblem

•• Example:Example: male Type O (ii) x female type AB (IAIB) IA IB

A B i I i I i 1/2 = IAi 1/2 = IBi i IAi IBi

85 CodominanceCodominance

QuestionQuestion:: IfIf aa boyboy hashas aa bloodblood typetype OO andand hishis sistersister hashas bloodblood typetype AB,AB, whatwhat areare thethe genotypesgenotypes andand phenotypesphenotypes ofof theirtheir parents?parents? boyboy -- typetype OO (ii)(ii) XX girlgirl -- typetype ABAB (I(IA IIB))

86 CodominanceCodominance

Answer:Answer:

IA i

IB IAIB Parents:Parents: genotypesgenotypes = IAi and IBi phenotypesphenotypes = A and B i ii

87 SexSex--linkedlinked TraitsTraits

TraitsTraits (genes)(genes) locatedlocated onon thethe sexsex chromosomeschromosomes SexSex chromosomeschromosomes areare XX andand YY XXXX genotypegenotype forfor femalesfemales XYXY genotypegenotype forfor malesmales ManyMany sexsex--linkedlinked traitstraits carriedcarried onon XX chromosomechromosome

88 SexSex--linkedlinked TraitsTraits Example:Example: EyeEye colorcolor inin fruitfruit fliesflies SexSex ChromosomesChromosomes

fruit fly eye color

XX chromosome - female Xy chromosome - male

89 SexSex--linkedlinked TraitTrait ProblemProblem Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) XRY x XrXr Remember: the Y chromosome in males does not carry traits. Xr Xr RR = red eyed Rr = red eyed XR rr = white eyed XY = male XX = female Y

90 SexSex--linkedlinked TraitTrait Solution:Solution:

Xr Xr 50% red eyed XR XR Xr XR Xr female 50% white eyed Y Xr Y Xr Y male

91 FemaleFemale CarriersCarriers

92 GeneticGenetic PracticePractice ProblemsProblems

93 BreedBreed thethe PP11 generationgeneration talltall (TT)(TT) xx dwarfdwarf (tt)(tt) peapea plantsplants

t t

T

T

94 Solution:Solution: talltall (TT)(TT) vs.vs. dwarfdwarf ((tttt)) peapea plantsplants t t

produces the T Tt Tt FF1 generationgeneration

T Tt Tt All Tt = tall (heterozygous tall)

95 BreedBreed thethe FF11 generationgeneration talltall (Tt)(Tt) vs.vs. talltall (Tt)(Tt) peapea plantsplants

T t

T

t

96 Solution:Solution: talltall ((TtTt)) xx talltall ((TtTt)) peapea plantsplants T t produces the F generation T TT Tt F2 generation 1/4 (25%) = TT 1/2 (50%) = Tt t Tt tt 1/4 (25%) = tt 1:2:11:2:1 genotypegenotype 3:13:1 phenotypephenotype

97 Pedigree Charts •Pedigree chart – a chart used to record the transmission of a particular trait or traits over several generations. (like a family tree)

98 Pedigree Chart

99 Questions Questions 1-3 page 607

100 Other Patterns of Inheritance •Pleiotrophic Genes – affect many different characteristics. Ex: Sickle cell anemia. A blood disorder. Normal hemoglobin has the allele HbA. Sickle cell occurs in individuals who have two copies of the mutated allele HbS. This mutation causes abnormally shaped hemoglobin that interlock with one another. People with sickle cell, are fatigued, weak and have an enlarged spleen. Often show signs of heart lung, and kidney failure.

101 Multiple Alleles

•Multiple Alleles – when trait are determined by more that two alleles. Most commonly seen trait is call the wild type. •Mutant – any allele of a gene other than the wild type allele.

Ex: fruit fly can have any one of four eye •colours. Red is the wild type, eyes may also be apricot, honey and white. They have two alleles for eye colour.

102 103 Review Questions •Page 478 Questions 1-8 (old text)

104 105 Environment and Phenotype •Himalayan rabbits have black fur when raised in low temperatures and white in high temperatures

106 Questions Questions 1-3 page 612

107 Dihybrid Crosses and Polygenic Traits •Dihybrid cross – a genetic cross involving two genes, each of which has more than one allele.

108 Dihybrid Crosses

109 Punnett Square

110 Probability and Dihybrid Crosses

P = # of ways that a given outcome can occur total # of possible outcomes

Questions page 615

111 Selective breeding

•Selective breeding – the crossing of desired traits from plants or animals to produce offspring with both characteristics

112 Selective Breeding

113 •Inbreeding – the process whereby breeding stock is drawn from a limited number of individuals possessing desirable phenotypes.

•Polygenetic traits – inherited characteristics that are determined by more than one gene

•Epistatic gene – a gene that masks the expression of another gene or genes.

114 Review Questions

•Page 483 Questions 9-11 (old text) •Questions 1-4 page 619

•Review Questions page 623- 625

115 Review Questions

•Page 489 Questions 12-14

116 Social Issue •Social Issue Page 491

117 Lab

118 119