2 What is Heredity?Female normal wingThe passing on of traits from one generation to the nextXP- generationMale double wingF1 – normal wing
3 Early Ideas about Heredity Chapter 9, Section 1: Pre-MendelEarly Ideas about HeredityBlending Theory (19th century):Each parent contributed “factors” that were blended in the offspringWhat was the problem with this theory?All individuals of a population would eventually look the same.Once blended, traits would never separate and show up in later generations.
4 Gregor Mendel (1822 – 1884) Augustinian monk who studied pea plants Chapter 9, Section 1: MendelGregor Mendel (1822 – 1884)Augustinian monk who studied pea plantsEstablished the particulate theory of hereditySignificance:Developed pure linesCounted results and kept statistical notes (data)His work remained undiscovered until 1903.
5 Why did he research pea plants? CharacterDominant TraitRecessive TraitMendel’s ResearchFlower ColorWhy did he research pea plants?PurpleWhiteThey are normally self-pollinated, but can be cross-pollinated.They have several qualitative traits that are easy to distinguishi.e.,Tall vs. ShortSelf PollinationFlower PositionSideTopSeed ColorYellowGreenSeed ShapeRoundWrinkledPod ShapeInflatedConstrictedPod ColorGreenYellowCross PollinationStem LengthTallDwarf
6 Watch this video clip, and see if you can explain why… Mendel’s ResearchRemoved stamens from purple flower.Transferred pollen from stamens of white flower to pistil of purple flower.Pollinated flower matured into a pod.Planted seeds from pod.Examined offspring: All purple flowers…Watch this video clip, and see if you can explain why…
7 Mendel’s Conclusions Law of Segregation Factors (genes) for a particular trait occur in pairsFor each trait, an organism inherits two genes, one from each parent.Dominant alleles mask recessive onesException 1: Incomplete DominanceException 2: Co-dominanceTwo alleles for each trait segregate (separate) during gamete production
8 Genes: The “factors” that control traits. Homologous pair of ChromosomesGenes: The “factors” that control traits.Law of Segregation:Factors for a particular trait occur in pairsAlleles: Different forms of a gene.Locus for Flower Color GeneAllele for White Flowers (p)Allele for Purple Flowers (P)Back to Mendel’s Conclusions
9 Each individual is diploid Each gamete is haploid WwororwwW = widow’s peakw = no widow’s peakWwwwEach individual is diploidDiploid: Containing a double-set of chromosomes (2n)Each gamete is haploidGamete: Reproductive cell (egg or sperm)Haploid: Containing a single-set of chromosomes (n)Law of Segregation:One version of each gene is inherited from each parentBack to Mendel’s Conclusions
10 P (Parent) Generation True-breeding parents Dominant alleles mask recessive onesP (Parent) Generation True-breeding parents(PP x pp)F1 (1st Filial) Generation Hybrid Offspring (Pp)What happened to the recessive traits?705 plants had purple flowersF2 (2nd Filial) Generation224 plants had white flowersWhat is the F2 ratio?705:224 3:1
11 P Generation F1 Generation F2 Generation PP:Pp:pp 1:2:1 3: 1 Dominant alleles mask recessive onesP GenerationPhenotype (Appearance)Purple FlowersWhite FlowersGenotype (Genetic Makeup)PPppGametesPpF1 GenerationPhenotype (Appearance)Purple FlowersGenotype (Genetic Makeup)PpGametesPpPunnett SquareF2 GenerationPPWhat is the Genotypic Ratio of the F2 Generation?PPppPP:Pp:pp 1:2:1PpPpppWhat is the Phenotypic Ratio of the F2 Generation?3:1
13 Vocabulary PracticeWe will now play “Got Gametes?” in order to practice understanding the following new terms: alleles, genotype, phenotype, homozygous, heterozygous
14 Vocabulary PracticeEach of you are haploid gametes carrying single alleles – for a trait.Your single letter can be combined with another single letter (i.e., Hh) to form a genotype in a diploid organism.You will observe a series of faces. Come to the front of the classroom if you think you have the right genotype to match the phenotype shown. Make sure to find the corresponding allele for the trait you represent!
19 How do you set up a Punnett square? Now you try!Example 1:Heterozygous short hair (____) X heterozygous short hair (____)HhHhHhHhHHHHhhHhHhGenotypic Ratio HH:Hh:hh1:2:1Phenotypic Ratio Short hair:long hair3:1hh
20 If you have a dominant phenotype (like purple flowers) how would you determine if it was homozygous (PP) or heterozygous (Pp)? What experiment would you design?Dominate alleles mask recessive onesDominant phenotype, unknown genotype: PP or Pp?Recessive phenotype, known genotype: ppWhat would your hypothesis be if the genotype was PP?What would your hypothesis be if the genotype was Pp?If PP, then all offspring purple:If Pp, then ½ offspring purple and ½ offspring white:PpPpPpPpPpppPpPpppPpPpppThis is called a test crossBack to Mendel’s Conclusions
21 P Generation F1 Generation F2 Generation Phenotype(s): Red and WhiteGenotype(s): CRCR and CWCWGamete of Red flower: CR Gamete of White flower: CWCRCWF1 GenerationPhenotype: PinkGenotype: CRCWGametes: CR and CWCRCWF2 GenerationException to Dominant Alleles Masking Recessive AllelesIncomplete Dominance: Pink SnapdragonsUse Root Letter “C” to designate incomplete dominance interactionCRCRCRCRCWCWCRCWCRCWCWCWBack to Mendel’s Conclusions
22 Back to Mendel’s Conclusions Exception to Dominant Alleles Masking Recessive Alleles: Co-dominance: Blood Types (video)Use root letter “I” for dominant alleles of equal strength and “i” for recessiveBack to Mendel’s Conclusions
23 This occurs in a process called meiosis: Back to Mendel’s ConclusionsLaw of Segregation:Two alleles for each trait segregate (separate) during gamete productionThis occurs in a process called meiosis:Specifically it is “crossing over,” which occurs very early during Prophase I of Meiosis and separation in Anaphase I and II
24 Mendel’s ConclusionsThe law of segregation followed one single trait at a time, such as seed color.What if two traits were followed, such as seed color and seed shape?Are these genes somehow connected (linked) and inherited together?
25 Following two traits: Seed shape and seed color GametesYRyrHypothesis: If the genes for seed shape and color are connected in some way,then the dominant R and Y alleles and the recessive r and y alleles will be matched sets in the gametes.F1YyRrOvaSpermYRYRyryrF2For the traits of seed shape and color, this hypothesis is NOT supported by experimental evidence
27 YyRr Now try to do it on your own! What are the phenotypic ratios? What are the genotypes of the P Generation?YYRRyyrrLaw of Independent AssortmentWhat does the P Generation pass on to F1?YRyrGametesF1 Phenotype?YyRrF1 Genotype?What does the F1 Generation pass on to F2?OvaSpermYRYRYrCombine the sperm and ova to produce the offspring in F2YrYYRRyRyRYYRrYYRryryrWhat do you expect the phenotype will be when YR and YR are combined?YyRRYYrrYyRRPhenotypic RatiosYyRrYyRrYyRrYyRr9/16Yellow & RoundWhat will the Genotype be when YR and YR are combined?YyrryyRRYyrr3/16Green & RoundyyRryyRr3/16Yellow & WrinkledNow try to do it on your own!yyrr1/16Green & WrinkledWhat are the phenotypic ratios?
28 Mendel’s Conclusion! FOIL Law of Independent Assortment: If the genes are not connected, then they should segregate independently. The alleles are randomly packaged into different gametes during meiosis(For example, genes for seed shape and color were not inherited together.)YyRr FOILYRYryRyr
29 Significance of Mendel’s Research Punnett Square was introduced as a tool to predict or determine the probability of an eventNow, let’s practice dihybrid crosses!
30 White board exercises One-trait cross The allele for the hairy trait is “H,” while the allele for the hairless trait is “h.”Make a cross between two homozygotes for each of these traits.
31 Punnett Square Exercise One-trait crossIn a population of Wisconsin fast plants, purple color is created by the pigment anthocyan. The gene that codes for this pigment is dominant (A), and without this pigment, the plant is green recessive (a).Predict the offspring from the cross of a purple homozygous plant and a green plant.What if the purple plant was heterozygous? How would the offspring be different?Purple plant: AAGreen plant: aaPurple plant: AaGreen plant: aaAaAaaAAaaaAaAaAa50% Purple50% Green100% PurpleaaAaAaaaGreen Purple
32 Punnett Square Exercise One-trait crossIn populations of hamsters, brown fur is dominant (B), and white fur is recessive (b).Predict the offspring from the cross of a white hamster and a brown hamster if the brown hamster's mother was white.Brown hampster: BbWhite hampster: bbBbOffspring50% brown mice50% white micebbBbbbBbbb
33 Punnett Square Exercise One-trait crossHenry VIII divorced six of his wives (two of whom were executed) for not bearing him any sons.Use Mendelian Genetics to prove to King Henry that it wasn’t his wives’ fault.Remember: Females are XX and Males are XY.Go to Test Crosses
34 White-board exercises Two-trait crossFollowing two traits:Kernel shape: Plump vs. withered (P and p) and Kernel color Red vs. yellow (R and r)Predict the cross between a homozygous recessive corn plant and a homozygous dominant corn plant.
35 Punnett Square Exercise Two-trait crossNow take the offspring from that cross, and self-pollinate that plant.What is the phenotypic ratio of this cross?
36 Punnett Square Exercise Two-trait crossMy pet guinea pigs (Joni and Chachi) are going to have little guinea pigs.What is the possibility that their offspring will have long hair, if I know that Joni and Chachi are heterozygous for the following traits?Black fur (B) White fur (b)Long hair (L) Short hair (l)