Mendel + Inheritance of Simple Traits_Ottolini_Biology

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  • Male and female reproductive parts are enclosed in the same flower
  • Mendel’
  • Mendel + Inheritance of Simple Traits_Ottolini_Biology

    1. 1. Chapter 8-1 The Origins of Genetics
    2. 2. Human Traits • Your physical traits resemble those of your parents. • Heredity = the passing of traits from parents to offspring
    3. 3. Gregor Johann Mendel • Mendel was an Austrian monk who conducted breeding experiments with garden peas. • Developed rules which accurately predict patterns of heredity • Genetics = the branch of biology that focuses on heredity
    4. 4. T.A. Knight • Also studied heredity in pea plants • Cross= mate or breed two individuals • Crossed purple-flowered garden peas with whiteflowered garden peas
    5. 5. Knight vs. Mendel Qualitative vs. Quantitative • Mendel counted the number and kind of offspring from each pea cross
    6. 6. Useful Features in Peas 1. Many traits that have two clearly different forms (no intermediate forms) Mating can be easily controlled 2. – – 1. Self-fertilization Cross-fertilization Small, grows easily, matures quickly & produces many offspring
    7. 7. Self-Pollination
    8. 8. Cross-Pollination
    9. 9. Nature’s Pollinators • Insects (bees) • Vertebrates (birds & bats) • Wind • Water
    10. 10. Mendel’s Observations: Traits are Expressed as Simple Ratios • First experiments involved monohybrid crosses • Monohybrid cross = a cross that involves one pair of contrasting traits
    11. 11. Mendel’s Experiments: Step #1 • Self-pollinate each pea plant for several generations • True-breeding= all offspring display only one form of a particular trait • P generation = parental generation, the first two individuals crossed in a breeding experiment
    12. 12. Mendel’s Experiment: Step #2 • Cross-pollinate the P generation plants with contrasting forms of a trait • F1 generation = the first filial generation, the offspring of the P generation • Characterize and count plants
    13. 13. Mendel’s Experiment: Step #3 • Allow the F1 generation to self-pollinate • F2 generation = the second filial generation, the offspring of the F1 generation plants • Characterize and count plants
    14. 14. Mendel’s Results • F1 generation showed only one form of the trait (e.g. purple flowers) – The other form of the trait disappeared (e.g. white flowers) – Reappeared in the F2 generation • 3:1 ratio of the plants in the F2 generation
    15. 15. Expressing Ratios: Mendel’s F2 Generation 705 purple-flowered plants; 224 white-flowered plants • Reduce the ratio to its simplest form: 705/224 = 3.15 Purple 224/224= 1 White – Ratio can be written in a few different ways: • 3:1 • 3 to 1 • 3/1

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