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Exercise 13:Reproduction

Exercise 13:Reproduction. Meiosis Spermatogenesis Oogenesis Ovarian cycle Uterine cycle Fertilization Embryonic and fetal development. Meiosis.

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Exercise 13:Reproduction

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  1. Exercise 13:Reproduction Meiosis Spermatogenesis Oogenesis Ovarian cycle Uterine cycle Fertilization Embryonic and fetal development

  2. Meiosis • the process of nuclear division within a cell that involves in a reduction of chromosome number from diploid to haploid, resulting in gamete formation • Human somatic (body) cells have 46 chromosomes • 22 pairs of autosomes and 2 sex chromosomes • XX in females, XY in males • Human gametes (sex cells – eggs and sperm) have 23 chromosomes • Sperm cells carry either an X or a Y

  3. Meiosis • Of the 46 chromosomes, there are 23 kinds - 2 copies of each kind • One copy from mother, one from father, coming together when a sperm fertilizes an egg • The 2 copies are called homologous chromosomes – they carry the same genes (although they might vary in the version – different alleles) • Exception: X and Y, although paired in males, are not considered homologous

  4. Meiosis • First: review of mitosis • Prior to mitosis • Replication of DNA • 46 chromosomes all copied • Each copy = chromatid • ‘sister’ chromatids held together at centromere

  5. Replicated chromosome

  6. Review of Mitosis • Stages of mitosis • Prophase: chromosomes condense and nuclear membrane breaks down; mitotic spindle forms • Metaphase: chromosomes align at equator • Anaphase: chromosomes divide • Telophase: chromosomes unpack; nuclear membranes reassemble

  7. Review of Mitosis

  8. Stages of Meiosis • Prior to meiosis: DNA replication, resulting in 46 chromosomes each with 2 sister chromatids held together at centromeres • Meiosis occurs in 2 phases: • Meiosis I: Reduction division • Separation of homologous chromosomes • Chromosome number now 23 • Each chromosome still has 2 sister chromatids • Meiosis II: Mitotic division • Separation of sister chromatids

  9. Meiosis I • In Prophase I, the homologous chromosomes pair up • This ensures that each daughter cell winds up with exactly one copy of each of the 23 kinds • The sister chromatids of the 2 chromosomes make 4 total copies of each DNA strand – a tetrad • While paired up, they entwine (synapsis) and can break and reform, swapping parts (chiasmata and crossing over)

  10. Stages of Meiosis I synapsis chiasma

  11. Stages of Meiosis I

  12. Stages of Meiosis II

  13. Products of Meiosis • Four daughter cells • Haploid (23 chromosomes) • Each has one copy of each kind of chromosome • Identical, except for 2 things: • In males, half X, half Y sex chromosomes • Crossing over results in different combinations of alleles

  14. Spermatogenesis

  15. Testis: Low Power • Seminiferous tubules: spermatogenesis • Interstitial cells: produce testosterone

  16. Spermatogenesis

  17. Spermatogenesis

  18. Spermatogenesis

  19. Oogenesis

  20. Ovary • Ovarian cycle • Follicular stage • Luteal stage • Follicles secrete estrogens and house egg • Primordial • Primary • Secondary • Mature

  21. Ovarian Cycle

  22. Ovary: Low Power

  23. Ovary: Early stages

  24. Ovary: Mature Follicle

  25. Ovary: Mature Follicle structures

  26. Ovary: Corpus Luteum

  27. Ovary: Corpus Luteum

  28. Uterine cycle • Corresponds with Ovarian Cycle • Synchronized by ovarian hormones • Menstrual phase • Proliferativie phase • Corresponds to ‘diestrous’ in other mammals • Secretory phase • Corresponds to ‘estrous’ in other mammals

  29. Uterus: Diestrous

  30. Uterus: Diestrous

  31. Uterus: Estrous

  32. Uterus: Estrous

  33. Embryonic and fetal development • EmbryologyReproduction.ppt

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