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Sexual Reproduction

Sexual Reproduction. Cellular Reproduction. There are 2 types of reproduction: Asexual Reproduction Sexual Reproduction. Cellular Reproduction. Asexual Reproduction (5 phases) 1 mother cell divides into 2 daughter cells Daughter cell is identi cal to its mother

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Sexual Reproduction

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  1. Sexual Reproduction

  2. Cellular Reproduction There are 2 types of reproduction: • Asexual Reproduction • Sexual Reproduction

  3. Cellular Reproduction • Asexual Reproduction (5 phases) • 1 mother cell divides into 2 daughter cells • Daughter cell is identical to its mother • Interphase + Mitosis • All human cells have46 chromosomes called “DIPLOID cells” • Produce SOMATIC cells(not sexual cells)

  4. Cellular Reproduction 2. Sexual Reproduction (9 phases) • 1mother cell divides into4daughter cells • Daughter cells have ½ the chromosomes of their mother (23) “HAPLOID cells” • Interphase + Meiosis I + Meiosis II • Crossing over of genetic material often occurs. • SEXUAL cells (egg and sperm) known as “gametes”

  5. Vocabulary

  6. Gametes ~ Another name for eggsand sperm ~ They are haploid (In humans, that is 23 chromosomes) ~ They are sexual cells ~ They are produced by sexual reproduction

  7. Homologous Chromosomes • A pair of chromosomes (maternal and paternal)that have similar/identical shapes andsizes. • Have genesfor the same characteristics (ie: eye color). • Eachlocus(geneposition) controls the same traitand is inthe same place on homologous chromosomes.

  8. Homologous Chromosomes chromatids chromatids Vocabulary tetrad

  9. Vocabulary Sperm + egg = zygote

  10. Eye color Eye color Hair color Hair color Paternal Locus Maternal Homologous Chromosomes

  11. Remember…  Interphase Prophase Metaphase Anaphase Telophase Asexual Reproduction Mitosis

  12. Sexual Reproduction • There are 3 major steps: ~ Interphase ~ Meiosis I ~ Meiosis II

  13. Interphase Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II Sexual Reproduction Meiosis

  14. 2n=46 4n=92 2n=46 meiosis I Meiosis in Humans n=23 AfterInterphase n=23 4 haploid gametes (n) n=23 n=23 diploid (2n) meiosis II

  15. Video • Meiosis

  16. Interphase (4n = 92) • Same as Interphase in Mitosis • Chromosome replication, growth and preparation (chromatin rolls etc) • Each of the replicated chromosomes possesses2chromatideswhich are attachedat theircentromere.

  17. Interphase (4n = 92) • We can see the nucleolus and the nuclear membrane. There are 92 chromosomes (46 pairs!!) Nuclear membrane Chromatine Cell membrane Nucleolus

  18. Meiosis I (4 phases) ~ Prophase I ~ Metaphase I ~ Anaphase I ~ Telophase I

  19. Prophase I (4n = 92) • 2 homologous chromosomes combine. This combination is called a TETRADXX • Spindle fibers grow, and attach to each side of the tetrad • Thenuclearmembraneand thenucleolusboth disappear

  20. Spindle fibers centrioles Prophase I (4n = 92)

  21. Crossing Over • DuringProphase I • One chromatid of each chromosome crosses over with the chromatid of the other chromosome. • The result is anexchangeof their genetic material

  22. Crossing Over The exchangeof sections ofhomologouschromosomes in aTETRAD. Maternal chromo Paternal chromo

  23. Metaphase I (4n = 92) • Spindle fibers pull on the tetrads, and align them in the centre of the cell.

  24. Metaphase I (4n = 92)

  25. Anaphase I (4n = 92) • Thetetrads separate and homologouschromosomes travel to the poles. • Homologues chromosomes are still attached by their centromeres.

  26. Anaphase I (4n = 92)

  27. Telophase I/Cytokenisis(2n = 46) • Each pole has a diploidnumber of chromosomes. • Cytokenisis - 2 diploids cells are formed. • Spindle fibers and centriolesdisappear. • The nuclear membrane sometimes reforms, and the nucleolus does not reform at this point.

  28. Telophase I (2n = 46) Cell division

  29. And the division continues!!!!

  30. Meiosis II (4 phases) ~ Prophase II ~ Metaphase II ~ Anaphase II ~ Telophase II

  31. Meiosis II Interphase II – does not exist ** Don’t forget!! This process is now occurring in both daughter cells created during Meiosis I **

  32. Prophase II (2n = 46) • Same as ProphaseinMitosis

  33. Metaphase II (n = 46) • Same as MetaphaseinMitosis

  34. Anaphase II (2n = 46) • Same as AnaphaseinMitosis • DON’T FORGET! Chromosomes are separated into chromatids.

  35. Telophase II/Cytokenisis (n = 23) • Same as TelophaseinMitosisEXCEPT n = 23 • The nucleolus and nuclear membrane reform • Cytokenisis Important: 4 haploid gametes areformed.

  36. Telophase II/Cytokenisis (n = 23)

  37. Animation!! Meiosis– McGraw-Hill animation

  38. Let’s review!!!

  39. Comparison of mitosis and meiosis

  40. Mitosis vs Meiosis

  41. Mitosis vs Meiosis

  42. Meiosis

  43. La mitose vs la méiose

  44. Attention!!!!!!!!!!!!! • Female meiosis is somewhat different. 4 gametes are initially created, but Cytokenisis is UNEQUAL. In this case, ONE GAMETE survives, and the other 3 are not viable.

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