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Introduction to the Case of the Mysterious Snake

Introduction to the Case of the Mysterious Snake. To preserve the animations, please be sure to work through the slide show before editing; movements will not appear on the slide itself – only during a slide show Notes about what to say are included on the slide notes area.

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Introduction to the Case of the Mysterious Snake

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  1. Introduction to theCase of the Mysterious Snake To preserve the animations, please be sure to work through the slide show before editing; movements will not appear on the slide itself – only during a slide show Notes about what to say are included on the slide notes area

  2. Professor Chiszar’sBig Surprise I had a photo of Prof. Chiszar in his lab, but the url is no longer available – I suggest adding a photo of someone handling snakes in a lab setting snakes Include a nice photo of a timber rattlesnake

  3. For a nice photo, see: http://animals.timduru.org/dirlist/snake/TimberRattlesnake_01-OnSand.jpg Timber rattlesnakeCrotalushorridus http://animals.timduru.org/dirlist/snake/TimberRattlesnake_01-OnSand.jpg

  4. Timber rattlesnake: Crotalushorridus For a nice video see http://www.youtube.com/watch?v=EMaBH7EKYMU The newborn snake pops out at about 2:30 on the video http://www.youtube.com/watch?v=EMaBH7EKYMU

  5. Timber rattlesnake: Crotalushorridus For an interesting video see: http://www.youtube.com/watch?v=y7B8L47jPD0 http://www.youtube.com/watch?v=y7B8L47jPD0

  6. Professor Chiszar’s big surprise For an nice photo see: http://www.bbc.co.uk/nature/adaptations/Ovoviviparity http://www.bbc.co.uk/nature/adaptations/Ovoviviparity

  7. One more surprise! It’s a boy!

  8. What would you like to ask Prof. Chiszar about this baby snake?

  9. Where do babies come from? • Ultimately: from cells • How do cells reproduce? Mitosis

  10. A Primer on Basic Features of Mitosis & Meiosis To preserve the animations, please be sure to work through the slide show before editing

  11. mitosis • Metaphase: homologous chromosomes independently line up • Produces two genetically identical nuclei (two genetically identical daughter cells after cell division)

  12. nucleus cell nucleus

  13. nucleus

  14. nucleus

  15. nucleus

  16. nucleus Original nucleus Daughter nucleus Daughter nucleus

  17. Could the baby snake be produced by mitosis?

  18. Well, where do baby snakes usually come from? For a nice photo of fertilization, see http://www.webmd.com/baby/ss/slideshow-conception http://www.webmd.com/baby/ss/slideshow-conception

  19. meiosis • DNA replicates once, but cell divides twice • First meiosis: duplicated, homologous chromosomes pair up at metaphase so each cell gets one set of duplicated chromosomes • Second meiosis: duplicated chromosomes line up independently at metaphase so each cell gets one sister chromatid (i.e. all cells are haploid and have only one copy of each chromosome) • Produces gametes with one set of chromosomes • Four gametes (sperm) or one big gamete (egg) & three tiny cells called polar bodies

  20. cell nucleus nucleus

  21. nucleus

  22. nucleus

  23. nucleus

  24. nucleus nucleus nucleus nucleus

  25. Mitosis Meiosis Cell division Cell division Cell division Cell division Cell division 2X

  26. meiosissex chromosomes

  27. X Y XY, male

  28. X Y

  29. X X Y Y

  30. X X Y Y

  31. X X X Y Y Y Y X X Y

  32. Mitosis Meiosis Genetic Sex Determination In Mammals X X X X X Y Y Y Cell division Cell division X X X X X X X Y Y Y X X Cell division Cell division Cell division 2X X Y X X Y Y X X X X

  33. Meiosis Mitosis Genetic Sex Determination In Birds,Reptiles Z Z Z Z Z W W W Cell division Cell division Z Z Z Z Z Z W W Cell division Cell division Z W Cell division 2X Z Z Z W Z Z W W Z Z Z Z

  34. Parthenogenesis in Vertebrates • Production of offspring from unfertilized eggs

  35. Some Variations in Vertebrate Reproduction Parthenogenesis Gynogenesis Hybridogenesis Homologs A b a B M1 M2 (P1 P2) (P3 P4) M1 M2 M1 M2 M1 P1 P1 P2 P3 P4 Defective Meiosis Defective meiosis Fertilization Fertilization Defective meiosis M1 M2 M1 P1 or P2 P3 or P4 Haploid egg (paternal genome eliminated) Diploid egg Paternal genome eliminated Haplotype Haplotype M1 M2 M1 M2 M1 P3 or P4 Diploid egg Development Development Development M1 M2 M1 M2 M1 P3 or M1 P4 Diploid egg Diploid egg

  36. Parthenogenesis in Vertebrates Where might meiosis “go wrong” so that a diploid egg cell is produced?

  37. Mitosis Meiosis A A A A A A B b b B AA, Bb B B Cell division Cell division Genotype of Diploid Parent Cell b b A A A A A A A A 2X A A b b B B B B b b Cell division Cell division Cell division AA, Bb A B A B A b A b A b A b A B A B

  38. Bonus slides – showing chromosomes with alleles

  39. mitosiswith alleles

  40. A A b B AA, Bb

  41. A A A A b b B B

  42. A A A A b b B B

  43. AA, Bb A A A A B b A A AA, Bb AA, Bb b b B B

  44. meiosiswith alleles

  45. A A B b AA, Bb

  46. A A b B

  47. A A A A b b B B

  48. A A A A b b B B

  49. A A A A AA, Bb b b B B A, b A, b A, B A, B

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