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
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 Follicles secrete estrogens and house egg
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 Menstrual phase
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