Chapter 11 -- Basic Genetics. Inheritance Gregor Mendel 1822-1884.

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Slide 1Chapter 11 -- Basic Genetics Slide 2 Inheritance Slide 3 Gregor Mendel 1822-1884 Slide 4 Mendels pea garden in Brno Slide 5 Verhandlungen des naturforschenden Vereines in Brnn. Brnn: Vereines, 1865. Mendels paper Slide 6 Why did Mendel choose peas? Slide 7 Mendels Peas Slide 8 Two Characters Seed Coat Flower color Slide 9 Two traits per character Rough Smooth Slide 10 Two traits per character Purple flowers White flowers Slide 11 Traits are alternative forms of characters white or purple smooth or rough Slide 12 Brother Mendel! We grow tired of peas! Slide 13 Slide 14 Controlling the mating Slide 15 No question as to parentage of offspring Slide 16 Compare Slide 17 1. Start with true breeding plants. 2. Cross alternative forms among these true- breeders. Mendels experimental design Slide 18 P Generation (true-breeding parents) F 1 Generation (hybrids) F 2 Generation Purple flowers White flowers All plants had purple flowers Slide 19 Slide 20 3. Allowed progeny (F1) to self-fertilize and examined offspring 4. Count the number of offspring of each type Mendels experimental design Slide 21 P Generation (true-breeding parents) F 1 Generation (hybrids) F 2 Generation Purple flowers White flowers All plants had purple flowers Slide 22 Monohybrid crosses: examining one trait at a time What Mendel found- monohybrid crosses Slide 23 P Generation (true-breeding parents) F 1 Generation (hybrids) F 2 Generation Purple flowers White flowers All plants had purple flowers Monohybrid Cross Slide 24 What Mendel found F1 generation P Generation (true-breeding parents) F 1 Generation (hybrids) Purple flowers White flowers All plants had purple flowers Slide 25 P Generation (true-breeding parents) F 1 Generation (hybrids) F 2 Generation Purple flowers White flowers All plants had purple flowers F1 x F1 Slide 26 F2: purple and white 705 purple flowered plants 224 white flowered plants 3:1 ratio What Mendel found F2 generation Slide 27 F 1 Generation (hybrids) All plants had purple flowers F2 Generation 705 purple 224 white 3:1 ratio Slide 28 Mendels 7 pea traits Slide 29 1. Alternative versions of genes lead to variations in inherited characters. Alternative versions are called alleles 2. Each individual receives 2 alleles. homozygotes: 2 copies of identical allele heterozygotes: two different alleles Mendels model Slide 30 3. In heterozygotes only the dominant form of allele will be expressed. genotype: alleles present phenotype: physical appearance 4. Alleles segregate from one another into gametes (Law of segregation) Mendels model Slide 31 Allele for purple flowers Homologous pair of chromosomes Allele for white flowers Locus for flower-color gene Chromosomes, genes and alleles .. Slide 32 Genes control characters e.g., flower color Slide 33 Genes control characters Traits are alternative forms of characters e.g., white or purple Slide 34 Traits are alternative forms of characters Alleles are alternative forms of a gene Genes control characters Slide 35 Slide 36 Human Chromosomes Slide 37 Genes Alleles and Slide 38 Variation within a population Slide 39 Capital letter for dominant allele; lower case letter for recessive allele Example flower color: P = dominant allele p = recessive allele Mendel used symbols to interpret results Slide 40 Phenotype: purple Genotype: PP or Pp Slide 41 Phenotype: white Genotype: pp Slide 42 Phenotype Purple 3 Genotype PP (homozygous Pp (heterozygous Pp (heterozygous pp (homozygous 1 2 1 Ratio 1:2:1 White Ratio 3:1 1 Slide 43 Cross plant with unknown genotype with homozygous recessive The testcross Slide 44 The Punnett square Reginald C. Punnett Slide 45 Slide 46 PP x pp p p P P Pp Slide 47 Dominant phenotype, unknown genotype: PP or Pp? If PP, then all offspring purple: pp P P Pp If Pp, then 1 2 offspring purple and 1 2 offspring white: pp P P pp Pp Recessive phenotype, known genotype: pp The testcross Slide 48 Different types of Inheritance Slide 49 Dominant - Recessive Slide 50 purple Pp PP white pp Slide 51 Incomplete Dominance Slide 52 Incomplete dominance When alleles are not fully dominant or fully recessive in heterozygotes Slide 53 Multiple Alleles: ABO Blood Group Codominance No single allele is dominant Each allele has its own effect. Slide 54 Codominance Slide 55 Type A: adds galactosamine I A I A, I A i Type B: adds galactose I B I B, I B i Type AB: adds galactosamine and galactose I A I B Type O: no sugar added ii Multiple Alleles: ABO Blood Group Slide 56 ABO Blood Groups Slide 57 Pleiotropic Effects One allele have multiple effects Slide 58 Environmental effects Slide 59 THE CHROMOSOMAL BASIS OF INHERITANCE Slide 60 Chromosomes and Mendelian Inheritance Slide 61 Allele for purple flowers Homologous pair of chromosomes Allele for white flowers Locus for flower-color gene Chromosomes, genes and alleles .. and loci Slide 62 Thomas Hunt Morgan (1866 1945) Drosophila Slide 63 Slide 64 Human Chromosomes Slide 65 Sex Linkage XX female XY male Slide 66 Human sex chromosomes Slide 67 Color blindness Sex Linked traits Male pattern baldness Slide 68 Chromosomal problems Slide 69 Slide 70 Slide 71 Slide 72 Slide 73 Klinefelter syndrone Slide 74 Recessive genes can be carried without being expressed Slide 75 Queen Victoria and hemophilia Slide 76 Slide 77 Sickle cell anemia Slide 78 Slide 79 Slide 80 Slide 81

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