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SMATH #14

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SMATH #14

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  1. -Cans project widely known as Tokyo underground flood tunnels is the networks of tunnels 6.4 kilometers (four miles) long built deep under the ground in the Tokyo suburbs. All this infrastructure is dedicated to prevent flooding when Tokyo metropolitan area rivers are overfilling during the rain seasons or in case of typhoons. SMATH #14

  2. Introduction to Genetics Notes CH 11 Go to Section:

  3. Slide # 2 Introductory Vocabulary • 1. Character: inheritable feature of an organism • Example of characters in pea plants: Plant height, flower color, seed color, seed shape • 2. Trait: variation in an inheritable feature

  4. Slide # 3 Introductory Vocabulary • 3. Heredity: transfer of traits from parent to offspring a. Inherited traits: traits received from parents b. Acquired traits: traits done to an organism that alter the appearance of the organism • 4.Genetics: study of heredity • 5. Pure breeding: producing same traits each generation • 6. Hybrid: offspring from mating 2 different purebreds Character: Stem height Traits: Tall or dwarf

  5. Slide # 4 Gregor Mendel: The Father of Genetics • 1. Gregor Mendel: 1822-1884 Austrian monk • Did genetics (breeding) experiments on garden pea plants. • 1866: Published paper on experiments Gregor Mendel

  6. The Monastery Garden: Eight Years of Pea Experiments The Monastery Garden with the greenhouse which Gregor J. Mendel, O.S.A., had built in 1870. Its appearance before 1902. Courtesy of Villanova University Archives. Gregor J. Mendel, O.S.A., experimental garden (35x7 meters) in the grounds of the Augustinian Monastery in Old Brno. Its appearance before 1922. Courtesy of Villanova University Archives.

  7. Slide # 5 Why Mendel Chose Pea Plants Cut stamens (holds pollen) off of one flower • Mendel chose pea plants for several reasons • Grow quickly; grow many generations in short time • Produce many offspring • Have distinct traits • Tall or dwarf • Yellow or green seeds • Could strictly control pollination Brushed pollen from a 2nd flower onto carpel (holds eggs) of 1st flower Carpel develops into a pea pod.

  8. Experiments with Pea PlantsThe distinct “either or“ traits. • Seed shape • (Smooth or wrinkled)

  9. Slide # 6 Purple Flowers X White Flowers Mendel’s Experiment • 1. Began with purebreeding parents. • 2. All traits were the same in BOTH plants EXCEPT the trait being crossed. • 3. All F1 generation flowers (first generation) had purple flowers – it appeared as though white trait was lost! 4. Allowed 2 F1’s to self pollinate. In F2 generation, Mendel counted 705 purple flowered plants and 224 white flowered plants. (3 purple:1 white ratio) 5. The white flower trait was not lost; it was masked by the purple flower trait!

  10. Question: What were the offspring of this P cross between a white and a purple flowering pea plant? • The F1 generation plants all had purple flowers. • Question: What happens when the F1 generation of pea plants are allowed to self-fertilize? • The white trait reappeared! • Question: What was the ratio for purple to white flowering plants in the F2 generation? • 3 purple :1 white

  11. Slide # 7 Seed Shape Seed Color Flower Position Plant Height Pod Shape Pod Color Seed Coat Color Round Gray Green Smooth Yellow Axial Tall Mendel Found a Similar Pattern in Other Traits P Wrinkled Terminal Green White Yellow Constricted Short F1 Round Gray Yellow Smooth Green Tall Axial Only one trait showed up in F1’s; & both traits appeared in F2’s at a 3:1 ratio. Go to Section:

  12. Slide # 9 Conclusions made by Mendel: • 1. Each parent MUST contribute one gene for each trait to the offspring. • Evidence: F2’s had white flowers (present but hidden in F1 generation.) • 2. Each parent must have two copies of a gene; and can have two different versions of that gene called alleles at the same time. • -- Evidence: F2’s had white flowers both parents must have had at least one white allele! • Dominant: allele that is expressed when 1 or both are present (capital letter) • Recessive: allele that is masked by presence of dominant allele (lower case) a. The individual MUST have both recessive alleles to show the recessive trait The F1 purple flowering plants must have a second hidden gene for white flowers!

  13. Slide # 8 Homologous Chromosomes MOM FROM FROM DAD Alleles • 1. Alleles: alternate forms of a gene or trait a. Parents may have two of the same alleles or two different alleles b.Homozygous: having 2 identical alleles c. Heterozygous: having 2 different alleles • 2. Alleles are located on chromosomes Every organism has two copies of the same gene. One copy came from MOM in her egg, the other gene copy came from DAD in his sperm. This plant has 2 different alleles for the flower color character.

  14. Homologous Chromosomes: • -are similar gene carrying chromosomes from the opposite-sex parents.

  15. Gene Chromosome Homologous Pair Allele Threadlike structures made of DNA found in nucleus Unit of inheritance One form of a gene Two chromosomes that carry the same genes, but just different versions of those genes. Vocabulary Review Match these in your head, be ready to share.

  16. Hybrid Slide # 10 Phenotypes: Purple & White Genotypes: PP x pp Mendel Solves the Genetics Puzzle Purebred • Mendel reasoned that each parent must have 2 possible alleles to contribute • Genotype: the alleles the organism has (two letters) • Phenotype: physical appearance of an organism • Mendel reasoned that the two alleles separated when gametes (sex cells like eggs) formed. • Mendel also reasoned that the alleles paired up again during fertilization(joining of egg &sperm) Gametes: P ~ p Fertilization: Pp Phenotype of F1: All Purple Genotype of F1: All Pp

  17. To show possible outcomes of genes the new generation will have We use: Gene diagrams or Punnett Squares

  18. Gene Diagram – Flower color Alleles- P = Purple flower p = White flower All genes occur in pairs – so 2 alleles affect a characteristic – possible combinations are; genotypes PPPppp Phenotypes PURPLE PURPLE WHITE

  19. parent Male female Gene Diagram – Flower color Pp Pp gamete P p P p Offspring genotype Pp pp Pp PP PurpleWhitePurplePurple Phenotype 3 purple : 1 white

  20. Punnett Square • Another method of showing crosses

  21. Punnett Square • Determine what the alleles are. P=purple p=white • Parent genotypes are determined. --Both are Pp • Parent’s possible gametes are determined and placed one next to -or above each box. Pp Purple male Complete the Cross 3 purple and 1 white offspring 3:1 chance with these parents P p Pp PP P Pp purple female p Pp pp

  22. Slide # 11 Genotype of F1: Pp x Pp Why the White Flowers Reappeared in the F2’s Gametes: ½ P ½ P ½ p ½ p F2 Genotypes: 1 PP: 2 Pp: 1 pp F2 Phenotypes: 3 Purple : 1 White

  23. In Summary, Mendel’s Work Showed: • Each parent contributes one allele for eachtrait. • The two alleles of each trait separatefrom each other when gametes form (in meiosis) and pair up again during fertilization. • Male’s (sperm) and female’s (egg) contribute equally. • Acquired traits are not inherited.

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