1. Reproduction Lecture-7 copyright cmassengale

2. Reproduction Sexual Reproduction Asexual Reproduction

4. Identical Daughter Cells Parent Cell Two identical daughter cells copyright cmassengale

8. Animation of Binary Fission copyright cmassengale

16. Meiosis Formation of Gametes (Eggs & Sperm) copyright cmassengale

21. Fertilization – “Putting it all together” 1n =3 2n = 6 copyright cmassengale

23. A Replicated Chromosome Gene X Homologs separate in meiosis I and therefore different alleles separate. copyright cmassengale Homologs (same genes, different alleles) Sister Chromatids (same genes, same alleles)

25. Meiosis: Two Part Cell Division Homologs separate Sister chromatids separate Diploid Diploid Haploid copyright cmassengale Meiosis I Meiosis II

26. Meiosis I: Reduction Division Early Prophase I (Chromosome number doubled ) Late Prophase I Metaphase I Anaphase I Telophase I (diploid) copyright cmassengale Nucleus Spindle fibers Nuclear envelope

28. Tetrads Form in Prophase I Homologous chromosomes (each with sister chromatids) Join to form a TETRAD Called Synapsis copyright cmassengale

30. Homologous Chromosomes During Crossing-Over copyright cmassengale

31. Crossing-Over Crossing-over multiplies the already huge number of different gamete types produced by independent assortment copyright cmassengale

32. Metaphase I Homologous pairs of chromosomes align along the equator of the cell copyright cmassengale

33. Anaphase I Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres . copyright cmassengale

34. Telophase I Nuclear envelopes reassemble. Spindle disappears. Cytokinesis divides cell into two. copyright cmassengale

36. Meiosis II: Reducing Chromosome Number Prophase II Metaphase II Anaphase II Telophase II 4 Genetically Different haploid cells copyright cmassengale

37. Prophase II Nuclear envelope fragments. Spindle forms. copyright cmassengale

38. Metaphase II Chromosomes align along equator of cell. copyright cmassengale

39. Anaphase II Sister chromatids separate and move to opposite poles . Equator Pole copyright cmassengale

40. Telophase II Nuclear envelope assembles. Chromosomes decondense. Spindle disappears. Cytokinesis divides cell into two. copyright cmassengale

41. Results of Meiosis Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome One allele of each gene Different combinations of alleles for different genes along the chromosome copyright cmassengale

42. Meiosis Animation copyright cmassengale

43. Gametogenesis Oogenesis or Spermatogenesis copyright cmassengale

45. Spermatogenesis in the Testes Spermatid copyright cmassengale

46. Spermatogenesis copyright cmassengale

48. Oogenesis in the Ovaries copyright cmassengale

49. Oogenesis copyright cmassengale Oogonium (diploid) Mitosis Primary oocyte (diploid) Meiosis I Secondary oocyte (haploid) Meiosis II (if fertilization occurs) First polar body may divide (haploid) Polar bodies die Ovum (egg) Second polar body (haploid) a A X X a X A X a X a X Mature egg A X A X

50. Comparing Mitosis and Meiosis copyright cmassengale

51. Comparison of Divisions copyright cmassengale Mitosis Meiosis Number of divisions 1 2 Number of daughter cells 2 4 Genetically identical? Yes No Chromosome # Same as parent Half of parent Where Somatic cells Germ cells When Throughout life At sexual maturity Role Growth and repair Sexual reproduction

54. Fertilisation

55. Fertilisation