1. 1 COMPARING MITOSIS AND MEIOSIS © 2007 Paul Billiet ODWSODWS

2. 2 COMPARING MITOSIS AND MEIOSIS © 2007 Paul Billiet ODWSODWS

3. 3 Control of mitosis:CYCLIN

4. 4 Eukaryotic cells?? The nucleus? Nuclear membrane Chromosomes…not chromosome…? All that ‘stuff’ in the cytoplasm?

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6. 6 Kinetochore (centromere)

7. 7 Chromosomes duplicate

8. 8 Eukaryotic cell cycle Cell is ‘born’ Duplicates DNA?? Grows to…size? Prepares to divide Divides=mitosis

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23. 23 Mitosis produces identical offspring (2N---2N)

24. 24 Importance??? Growth Replacement Cancer Regeneration of…

25. 25 Name stage of mitosis

26. 26 Name stage of mitosis

27. 27 Name stage of mitosis

28. 28 Name stage of mitosis

29. 29 Name stage of mitosis

30. 30 Name stage of mitosis

31. 31 Name stage of mitosis

32. 32 Name stage of mitosis

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34. 34 Meiosis – A Source of Distinction Why do you share some but not all characters of each parent? What are the rules of this sharing game? At one level, the answers lie in meiosis.

35. 35 Why do we need meiosis? Meiosis is necessary to halve the number of chromosomes going into the sex cellsMeiosis is necessary to halve the number of chromosomes going into the sex cells Why halve the chromosomes in gametes? At fertilization the male and female sex cells will provide ½ of the chromosomes each – so the offspring has genes from both parentsAt fertilization the male and female sex cells will provide ½ of the chromosomes each – so the offspring has genes from both parents

36. 36 2) Meiosis scrambles the specific forms of each gene that each sex cell (egg or sperm) receives. This makes for a lot of genetic diversity. This trick is accomplished through independent assortment and crossing-over. Genetic diversity is important for the evolution of populations and species.

37. 37 Meiosis Parent cell – chromosome pair Chromosomes copied 1 st division - pairs split 2 nd division – produces 4 gamete cells with ½ the original no. of chromosomes

38. 38 Meiosis – mouse testes Parent cell 4 gametes 1 st division 2 nd division

39. 39 The Stages of Meiosis:

40. 40 Figure 13.7 The stages of meiotic cell division: Meiosis I

41. 41 Meiosis II : Separates sister chromatids Proceeds similar to mitosisProceeds similar to mitosis THERE IS NO INTERPHASE II !THERE IS NO INTERPHASE II !

42. 42 Figure 13.7 The stages of meiotic cell division: Meiosis II

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44. 44 The Key Difference Between Mitosis and Meiosis is the Way Chromosomes Uniquely Pair and Align in Meiosis Mitosis The first (and distinguishing) division of meiosis

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46. 46 Meiosis I, Prophase I Leptotene –chromosomes become apparent Zygotene –homologous chromosomes pair synapsis form tetrad Pachytene –crossing over occurs Diplotene –chromosomes start to separate but held together by chiasmata Diakinesis –Further shortening of homologous chromosomes

47. 47 Oogonium Primary oocyte Secondary oocyte Polar Body I Fertilized Ovum Polar Body II Gametogenesi s Spermatogonium Primary spermatocyte Secondary spermatocytes 4 spermatids 4 spermatozoa

48. 48 Oogonium Primary oocyte Secondary oocyte Polar Body I Fertilized Ovum Polar Body II Males Spermatogonium Primary spermatocyte Secondary spermatocytes 4 Spermatids 4 spermatozoa Mitosis Throughout Life At Puberty Meiosis Complete in 64days

49. 49 Mitosis Fetal period Before or at birth After birth After puberty At fertilization Meiosis in progress Arrested in diplotene of Meiosis I Meiosis I complete Arrest at Metaphase II Meiosis II complete Oogonium Primary Oocyte Secondary Oocyte & Polar Body I Fertilized Ovum & Polar body II Females

50. 50 Differences in Gametogenesis Male Puberty 60-65 days 30-500 mitoses 4 spermatids 100-200 million /ejaculate Female Early embryonic development 10-50 years 20-30 1 ovum and polar bodies 1 ovum / menstrual cycle

51. 51 Female human embryo Stages in gonad 2 months gestation – oogonia start meiosis 5 months arrest in meiosis I (diplotene/dictyotene) 6 months chromosomes held together by chiasmata By puberty 100,000 remain Maximum 300-400 mature

52. 52 Meiosis – division error Chromosome pair

53. 53 Meiosis error - fertilization Should the gamete with the chromosome pair be fertilized then the offspring will not be ‘normal’. In humans this often occurs with the 21 st pair – producing a child with Downs Syndrome

54. 54 21 trisomy – Downs Syndrome Can you see the extra 21 st chromosome? Is this person male or female?

55. 15- تشابهات و اختلالات ژنتيكي پروكاريوتيكها و بوكار بوتيكها سيكل حياتي در رابطه با ژنها و كروموزومها 55