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Single Gene Traits: Earlobes

Single Gene Traits: Earlobes. phenotype : a product/trait resulting from a gene. Alleles. alternative forms of a gene we inherit 2 alleles of every gene (1 from mom, 1 from dad) . Alleles for Earlobe Shape:. Attached: recessive, f. Free: dominant, F.

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Single Gene Traits: Earlobes

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  1. Single Gene Traits: Earlobes phenotype: • a product/trait resulting from a gene

  2. Alleles • alternative forms of a gene • we inherit 2 alleles of every gene (1 from mom, 1 from dad)

  3. Alleles for Earlobe Shape: Attached: recessive, f Free: dominant, F

  4. gene: section of DNA that codes for earlobe shape

  5. 2 possible alleles: attached (f), free (F) OR f F

  6. But! You have 2 parents – each donated a chromosome Dad Mom OR OR AND f F f F

  7. Genotype • genotype: • the specific set of alleles contained in you

  8. Mom Dad ff OR OR Ff Ff FF f F f F

  9. Describing the allele combination: • homozygous: alleles are the same on homologous chromosomes (FF or ff) • heterozygous: alleles are different (Ff)

  10. Homologous chromosomes: - code for same set of genes - occur in pairs, 1 from each parent Dad Mom

  11. How many homologs of a given chromosome? • 2  Diploid (2n) • 1  Haploid (1n) • 3  Triploid (3n), etc. . . where n = number of different kinds of chromosomes

  12. Attached Free

  13. Attached Free recessive, f dominant, F

  14. Individually, build a set of chromosomes to reflect your genotype – draw them. Mom Dad f F

  15. Clicker: What is the correct representation for a free-lobed heterozygote who’s mother has attached lobes? B C A f F f f F F D E f F F f

  16. sister chromatids sister chromatids centromere

  17. Clicker: What is the correct representation for the duplicated state of: f F B A C E D

  18. Cells Must Divide For: • Growth (Mitosis) • Sex (Meiosis) • Copy DNA to ensure that each new cell gets the complete set

  19. Pair of unduplicated homologous chromosomes Gene of interest: hitchhiker’s thumb T = straight t = hitchhiker

  20. Hitchhiker

  21. Hitchhiker t t

  22. Non-hitcher?

  23. Non-hitcher T T t T OR

  24. Pair of unduplicated homologous chromosomes T t 1. Build these chromosomes in the duplicated state.

  25. Cell Division by Mitosis: • Produces identical “sister cells” • 1 diploid cell  2 diploid cells

  26. T t Pair of unduplicated homologous chromosomes Pair of duplicated homologous chromosomes t t T T

  27. Nucleus t t T T Cell Mitosis

  28. t t T T T T Mitosis t t

  29. Mitosis T T T T t t t t

  30. Cell Division by Meiosis: • Produces Gametes (sex cells) • 1 diploid cell  4 haploid cells • Two Divisions: • Meiosis I: Homologs Separate • Meiosis II: Sister Chromatids Separate

  31. Pair of unduplicated homologous chromosomes T t Build these chromosomes in the duplicated state -

  32. t t T T Meiosis I

  33. t t T T Meiosis I

  34. t t T T Homologs separate Meiosis I T T t t

  35. T T t t Meiosis II

  36. T T t t Meiosis II Sister Chromatids separate T T t t

  37. T T t t From a heterozygote parent, (genotype = Tt) 2 types of gametes formed: “T” or “t”

  38. Problem 1: Draw Meiosis for Pair 22 • Use your model to show exactly when and where the mistake occurred that resulted in the genotype for Trisomy. • Draw individually - consult with your group.

  39. Problem 2: Draw the Punnett Square and calculate the ratios of both phenotypes and genotypes for the offspring of: Cross 1: heterozygous female with an attached-lobed male.

  40. Making things a bit more complex: Meiosis with two genes found on two different chromosomes: keeping track of both the hitchhiker and the earlobes!

  41. Follow along in Mirkov: 2 chromosomes, 2 genes, each with 2 alleles t T F f

  42. Step 1: Chromosomes duplicate t t T T f F F f

  43. Step 2: Meiosis I: Homologs Separate t t T T F f F f

  44. Step 3: Meiosis I: Homologs Separate t t T T F f F f

  45. Step 4: Meiosis I: Homologs Separate  2 cells t t T T F F f f

  46. Step 5: Meiosis II: Sister Chromatids Separate t t T T f f F F

  47. Step 6: Meiosis II: Sister Chromatids Separate  4 cells T t T t F f F f

  48. What if homologs lined up differently at Meiosis 1? (Independent Assortment) t t T T How many different kinds of gametes could be formed? F f F f

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