Single Gene Traits: Earlobes

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

18. sister chromatids sister chromatids centromere

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

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

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

22. Hitchhiker

23. Hitchhiker t t

24. Non-hitcher?

25. Non-hitcher T T t T OR

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

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

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

29. Nucleus t t T T Cell Mitosis

30. t t T T T T Mitosis t t

31. Mitosis T T T T t t t t

32. 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

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

34. t t T T Meiosis I

35. t t T T Meiosis I

36. t t T T Homologs separate Meiosis I T T t t

37. T T t t Meiosis II

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

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

40. 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.

41. 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.

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

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

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

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

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

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

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

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

50. 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