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Chapter 9:1 Mendel’s Legacy

Chapter 9:1 Mendel’s Legacy. Gregor Johann Mendel. Born 1822: Austria Son of a peasant farmer At 21, entered monastery in Brunn, Austria Ordained into priesthood Studied math and science at University of Vienna Returned to monastery taught school and kept a garden. Experiments in Heredity

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Chapter 9:1 Mendel’s Legacy

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  1. Chapter 9:1 Mendel’s Legacy

  2. Gregor Johann Mendel • Born 1822: Austria • Son of a peasant farmer • At 21, entered monastery in Brunn, Austria • Ordained into priesthood • Studied math and science at University of Vienna • Returned to monastery taught school and kept a garden

  3. Experiments in Heredity • Garden Pea (Pisum sativum) Today Molecular Genetics:

  4. Garden Peas: Traits have 2 different forms

  5. Mating is easily controlled • Male and Female reproductive parts on same flower • Self-Fertilization • Cross pollinate

  6. Get Results Quickly • Plants are small, grow easily • Produce many offspring quickly

  7. Mendel’s Experiments: One contrasting trait • Garden pea was self-pollinated for several generations • Ensures True-Breeding: that all the offspring would display only one form of a trait • Parental Generation (P Generation) Example: All Purple Flowers All White Flowers

  8. 2. Crossed 2 P Generation plants that had contrasting traits Example: Purple Flower x White Flower • offspring gave 1st generation plants (F1 Generation)

  9. F1 generation self-pollinated - gave 2nd generation (F2 generation)

  10. Results • F1 plants showed only 1 form of trait (Purple) • Contrasting trait (white) disappeared • F2 plants-contrasting trait (white) appeared in some Ratio 3:1

  11. Conclusion • For each individual trait, an individual has two copies of the gene-one from each parent • There are alternative versions of genes (called alleles) • When two alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance Dominant: Trait that is expressed Recessive: Trait that is expressed only when both recessive alleles re present

  12. Conclusion cont. • Law of Segregation: pair of factors is segregated, separated, during the formation of gametes • Law of Independent Assortment: factors separate independently of one another during formation of gametes

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