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10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
10.2 mendelian genetics
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10.2 mendelian genetics

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  • 1. MendelianMendelian GeneticsGenetics Section 10-2Section 10-2 Pages 277-282Pages 277-282
  • 2. Gregor MendelGregor Mendel  Austrian monk and plant breederAustrian monk and plant breeder  He joined the monastery in 1843He joined the monastery in 1843  He carried out the first importantHe carried out the first important studies of hereditystudies of heredity  He was the first person toHe was the first person to succeed in predicting howsucceed in predicting how traits are transferred from onetraits are transferred from one generation to the next.generation to the next.  He published his findings inHe published his findings in 1866.1866.
  • 3. 3 Why peas?Why peas? Can be grown in a smallCan be grown in a small areaarea Produce lots ofProduce lots of offspringoffspring Produce pure plantsProduce pure plants when allowed to self-when allowed to self- pollinate for severalpollinate for several generationsgenerations Can be artificially cross-Can be artificially cross- pollinatedpollinated
  • 4. Why Peas?  Peas contain both gametes in the same flower  Pollen contains sperm produced by the stamen  Ovary contains eggs inside the flower  Pollen carries sperm to the eggs forPollen carries sperm to the eggs for fertilizationfertilization Self-fertilizationSelf-fertilization can occur in the samecan occur in the same flowerflower Cross-fertilizationCross-fertilization can occur betweencan occur between flowersflowers 4
  • 5. Genetic TermsGenetic Terms  Heredity – the passing on ofHeredity – the passing on of characteristics from parents tocharacteristics from parents to offspringoffspring  Genetics – the branch of biologyGenetics – the branch of biology that studies hereditythat studies heredity  Traits – characteristics that areTraits – characteristics that are inheritedinherited
  • 6.  PP11 generation – “parent” - the originalgeneration – “parent” - the original true-breeding parentstrue-breeding parents  FF11 generation – “filial” (or son orgeneration – “filial” (or son or daughter) offspring of the parentdaughter) offspring of the parent plantsplants  FF22 or “second filial generation” (oror “second filial generation” (or granddaughter or grandson)granddaughter or grandson) Mendel’s Experiments- Terms
  • 7. Mendel’s Experiments First Generation (FFirst Generation (F11)) Mendel grew seeds from a crossMendel grew seeds from a cross between green-seed and yellow-seedbetween green-seed and yellow-seed plants. All of the offspring had yellowplants. All of the offspring had yellow seeds.seeds. Second Generation (FSecond Generation (F22)) Mendel allowed the plants in the 1Mendel allowed the plants in the 1stst generation to self pollinate. ¾ of thegeneration to self pollinate. ¾ of the plants had yellow seeds and ¼ had green.plants had yellow seeds and ¼ had green.  Ratio of 3:1 (3 yellow to 1 green)Ratio of 3:1 (3 yellow to 1 green)
  • 8. 8
  • 9. 9
  • 10. AllelesAlleles Alleles- alternative form of a single geneAlleles- alternative form of a single gene passed from generation to generation.passed from generation to generation. Organisms have 2 genes that control each trait.Organisms have 2 genes that control each trait. These genes are located on theThese genes are located on the chromosomeschromosomes Dominant trait – appears in the FDominant trait – appears in the F11 generationgeneration Recessive trait – disappears in the FRecessive trait – disappears in the F11 generationgeneration
  • 11. A plant could have:A plant could have: 2 alleles for tallness (TT)2 alleles for tallness (TT) 2 alleles for shortness (tt)2 alleles for shortness (tt) 1 allele for tallness and 1 for shortness (Tt)1 allele for tallness and 1 for shortness (Tt) The 2 alleles are located on different copiesThe 2 alleles are located on different copies of a chromosome – one copy inheritedof a chromosome – one copy inherited from the female parent and one from thefrom the female parent and one from the male parentmale parent
  • 12. Rule of dominanceRule of dominance Pea plants that have at least 1 allele forPea plants that have at least 1 allele for tallness (TT or Tt) are tall because thetallness (TT or Tt) are tall because the allele for tallness is dominant over theallele for tallness is dominant over the allele for shortnessallele for shortness The only way a plant can be short is ifThe only way a plant can be short is if both height alleles are for a short plant (tt)both height alleles are for a short plant (tt)  HomozygousHomozygous – an organisms 2 alleles for– an organisms 2 alleles for a trait are the same (TT, tt)a trait are the same (TT, tt)  HeterozygousHeterozygous - an organisms 2 alleles for- an organisms 2 alleles for a trait are different (Tt)a trait are different (Tt)
  • 13. Phenotypes & GenotypesPhenotypes & Genotypes 2 organisms can look alike2 organisms can look alike but have different genebut have different gene combinationscombinations  PhenotypePhenotype – the way an– the way an organism looks andorganism looks and behaves (tall or short)behaves (tall or short)  GenotypeGenotype – the gene– the gene combination an organismcombination an organism contains (TT, Tt, tt)contains (TT, Tt, tt)
  • 14. Law of SegregationLaw of Segregation Law of Segregation- two alleles for each traitLaw of Segregation- two alleles for each trait separate during meiosis.separate during meiosis.  A TT plant can only produce T gametesA TT plant can only produce T gametes  A Tt plant can produce both T gametes andA Tt plant can produce both T gametes and t gametest gametes  A tt plant can only produce t gametesA tt plant can only produce t gametes The 2 alleles come together duringThe 2 alleles come together during fertilization.fertilization.
  • 15. TT Tt TT TT Tt Tt TtTTTT Tt T T T T t t T T segregation segregation fertilization fertilization gametes gametes P F1 F2 Segregation of Alleles
  • 16. Mendel’s CrossesMendel’s Crosses  Hybrid – offspring of parents that haveHybrid – offspring of parents that have different traitsdifferent traits  Mono – means oneMono – means one  Di- means twoDi- means two  Monohybrid crosses – the two parentMonohybrid crosses – the two parent plants differ by a single trait (height)plants differ by a single trait (height)  Dihybrid cross – parents differ by twoDihybrid cross – parents differ by two traits (height and color)traits (height and color)
  • 17. Monohybrid Cross (Seed color) Genotype- 1 YY, 2 Yy, 1yy or 1:2:1 Phenotype- 3 Yellow, 1 Green or 3:1
  • 18. Punnett SquaresPunnett Squares • 1905, Reginald Punnett, an English1905, Reginald Punnett, an English biologist, devised the shorthand way ofbiologist, devised the shorthand way of finding the expected proportions offinding the expected proportions of possible genotypes in the offspring of apossible genotypes in the offspring of a crosscross • Used to predict the possible genotypes ofUsed to predict the possible genotypes of offspringoffspring • In reality, you don’t get the exact ratio ofIn reality, you don’t get the exact ratio of results shown in the squareresults shown in the square
  • 19. Punnett Square-Monohybrid CrossPunnett Square-Monohybrid Cross
  • 20. Punnett SquarePunnett Square T t T TT Tt t Tt tt
  • 21. 22 • Trait: Seed ShapeTrait: Seed Shape • Alleles:Alleles: RR – Round– Round rr – Wrinkled– Wrinkled • Cross:Cross: RoundRound seeds xseeds x RoundRound seedsseeds • RrRr xx RrRr Monohybrid CrossMonohybrid Cross R r rR RR rrRr Rr Genotype:Genotype: RR, Rr, rrRR, Rr, rr PhenotypePhenotype: Round &Round & wrinkledwrinkled G.Ratio:G.Ratio: 1:2:11:2:1 P.Ratio:P.Ratio: 3:13:1
  • 22. 23 • Trait: Seed ShapeTrait: Seed Shape • Alleles:Alleles: RR – Round– Round rr – Wrinkled– Wrinkled • Cross:Cross: RoundRound seeds xseeds x RoundRound seedsseeds • RRRR xx RrRr Monohybrid CrossMonohybrid Cross R R rR RR RrRR Rr Genotype:Genotype: RR, RrRR, Rr PhenotypePhenotype: RoundRound GenotypicGenotypic Ratio:Ratio: 1:11:1 PhenotypicPhenotypic Ratio:Ratio: All alikeAll alike
  • 23. 24 • Trait: Seed ShapeTrait: Seed Shape • Alleles:Alleles: RR – Round– Round rr – Wrinkled– Wrinkled • Cross:Cross: WrinkledWrinkled seeds xseeds x RoundRound seedsseeds • rrrr xx RrRr Monohybrid CrossMonohybrid Cross r r rR Rr rrRr rr Genotype:Genotype: Rr, rrRr, rr PhenotypePhenotype: Round &Round & WrinkledWrinkled G. Ratio:G. Ratio: 1:11:1 P.Ratio:P.Ratio: 1:11:1
  • 24. 25 Law of Independent AssortmentLaw of Independent Assortment  Alleles forAlleles for differentdifferent traits are distributed totraits are distributed to sex cells (& offspring) independently of onesex cells (& offspring) independently of one another.another.  This law can be illustrated usingThis law can be illustrated using dihybriddihybrid crossescrosses..
  • 25. Dihybrid Cross (Seed color and shape) Phenotypes: 9 Round and Yellow 3 Wrinkled and Yellow 3 Round and Green 1 Wrinkled and Green or 9:3:3:1 ratio
  • 26. Punnett Square-Dihybrid Cross
  • 27. 28 Dihybrid CrossDihybrid Cross • Traits: Seed shape & Seed colorTraits: Seed shape & Seed color • Alleles:Alleles: R round r wrinkled Y yellow y green RrYy x RrYy RY Ry rY ryRY Ry rY ry RY Ry rY ryRY Ry rY ry All possible gamete combinationsAll possible gamete combinations
  • 28. 29 Dihybrid CrossDihybrid Cross RYRY RyRy rYrY ryry RYRY RyRy rYrY ryry
  • 29. 30 Dihybrid CrossDihybrid Cross RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RYRY RyRy rYrY ryry RYRY RyRy rYrY ryry
  • 30. 31 Dihybrid CrossDihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1
  • 31. 32 Summary of Mendel’s lawsSummary of Mendel’s laws LAWLAW PARENTPARENT CROSSCROSS OFFSPRINGOFFSPRING DOMINANCEDOMINANCE TT x ttTT x tt tall x shorttall x short 100% Tt100% Tt talltall SEGREGATIONSEGREGATION Tt x TtTt x Tt tall x talltall x tall 75% tall75% tall 25% short25% short INDEPENDENTINDEPENDENT ASSORTMENTASSORTMENT RrGg x RrGgRrGg x RrGg round & greenround & green xx round & greenround & green 9/16 round seeds & green pods9/16 round seeds & green pods 3/16 round seeds & yellow3/16 round seeds & yellow podspods 3/16 wrinkled seeds & green3/16 wrinkled seeds & green podspods 1/16 wrinkled seeds & yellow1/16 wrinkled seeds & yellow podspods

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