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Exercise 13:Reproduction

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Presentation on theme: "Exercise 13:Reproduction"— Presentation transcript:

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 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

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