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GENETICS

GENETICS. Unit 7. allele. How we inherit our genes Each human offspring inherits one maternal set of 23 chromosomes and one paternal set. Unlucky catch A baby inheriting two copies of the defective FMO3 gene will develop fish odor syndrome. Homozygous vs. Heterozygous. Homozygous

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GENETICS

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  1. GENETICS Unit 7

  2. allele

  3. How we inherit our genes Each human offspring inherits one maternal set of 23 chromosomes and one paternal set.

  4. Unlucky catch A baby inheriting two copies of the defective FMO3 gene will develop fish odor syndrome.

  5. Homozygous vs. Heterozygous

  6. Homozygous Heterozygous

  7. Family resemblance:

  8. Offspring resemble their parents because they inherit alleles from their parents.

  9. Heredity the passing on from one generation to another

  10. HEREDITY I AM the family face; Flesh perishes, I live on, Projecting trait and trace Through time to times anon, And leaping from place to place Over oblivion. The ears-heired feature that can In curve and voice and eye Despise the human span Of durance—that is I; The eternal think in man, That heeds no call to die. —Thomas Hardy, Moments of Vision and Miscellaneous Verses, 1917

  11. Some traits are controlled by a single gene

  12. One gene gives one trait most of the time

  13. HISTORY

  14. History of Genetics Timeline

  15. Older Ideas

  16. blending of their two parents’ traits via the blood

  17. Charles Darwin pangenesis

  18. Lamarck Inheritance of Acquired Characteristics

  19. Gregor Mendel: Mini-Biography

  20. Mendel didn’t do anything radically new, but simply applied methodical experimentation and scientific thinking

  21. Mendel chose a good organism to study: the garden pea. • relatively easy to fertilize manually by “pollen dusting” • easy to collect dozens or even hundreds of offspring from a single cross • pea plants are fast enough breeders that Mendel could conduct experiments that lasted for multiple generations

  22. Mendel chose to focus on seven easily categorized traits • flower color is purple or white • seed color is yellow or green • flower position is axial or terminal • pod shape is inflated or constricted • stem length is long or short • pod color is yellow or green • seed shape is round or wrinkled

  23. Mendel began his studies by first repeatedly breeding together similar plants until he had many distinct populations, each of which was unvarying for a particular trait

  24. In the mid-1800s, Gregor Mendel - how traits are inherited. • experimentation and hypothesis testing, -easily observed and categorized traits in garden peas. • Why was the pea plant a good organism with which to study heredity?

  25. PunnettSquares: Give Genotypes and Phenotype Ratios TtRr X TtRr Ttrr X ttrr ttRr X Ttrr TTrr X ttRR

  26. Mendel’s conclusions: • that the inheritance of each trait is determined by "units" or "factors" that are passed on to descendants unchanged - now called genes • that an individual inherits one such unit from each parent for each trait • that a trait may not show up in an individual but can still be passed on to the next generation

  27. Mendel's observations from these experiments can be summarized in two principles: • the principle of segregation • the principle of independent assortment

  28. Principle (Law) of Segregation:

  29. Principle (Law) of Independent Assortment:

  30. But wait…there’s more!

  31. Phenotype vs. Genotype

  32. Phenotype

  33. Genotype

  34. Chance is important • consequence of segregation • fertilization is a chance event

  35. Test Cross

  36. Test cross • In this test-cross, a homozygous white female alligator is bred with a normally colored male of unknown genotype. • The color of their offspring will help identify whether the male is homozygous dominant or heterozygous.

  37. Test Cross You mate a pigmented male alligator to a female albino alligator. The clutch of baby alligators includes both pigmented and albino individuals. What is the genotype of the father?

  38. In a test-cross, an individual with a dominant phenotype and an unknown genotype is mated with a homozygous recessive individual. • The phenotypes of the offspring reveal the unknown genotype.

  39. Pedigrees • In cross-pollinating plants that either produce yellow or green pea seeds exclusively, Mendel found that the first offspring generation (f1) always has yellow seeds.   However, the following generation (f2) consistently has a 3:1 ratio of yellow to green.

  40. Pedigrees • This 3:1 ratio occurs in later generations as well.   Mendel realized that this was the key to understanding the basic mechanisms of inheritance.

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