1. Chromosomes: the cellular basis of the instructions Mitosis - Meiosis

2. Diploid organism: two sets of chromosomes ( one from each parent)
Haploid organism: one set of chromosomes n

3. Germ cells: the cells that provide the continuity of life from generation to the next

4. Somatic cells: all the others

5. meiosis
Haploid egg
Haploid sperm
mitosis
Fertilization n n 2n

6. Mitosis

7. The cell cycle
Prophase
Metaphase
Anaphase
Telophase
Interphase

9. Prophase
Metaphase
Anaphase
Telophase 2N
Mitosis 2C 4C 4C 2C 2C

10. Mitosis: Sister chromatids
separate at anaphase

11. Homologous chromatids
Diploid cells 2C 4C 4C
Homologous chromatids 2C 2C
Diploid cells

12. Meiosis

13. 2N 2C
Prophase I 2N 4C 2N 4C 2N 4C 1N 2C 1N 2C 1N 1C

14. Prophase I 1. Leptotene 2.Zygotene 3.Pachytene 4.Diplotene
5.Diakinesis
Prophase I

15. Prophase I
5.Diakinesis
4.Diplotene

16. Crossing over Pairing of homologous chromosomes Chiasma formation
Breakage
and joining
Recombinant

17. Metaphase I
Anaphase I
Telophase I
Prophase II
Prophase I

18. Meiosis anaphase I :Homologous chromosomes separate
Reduction from diploid to haploid

19. Meiosis 1st division: reduction from diploid to haploid number of chromosomes two haploid cells

20. Meiosis 2nd division: like mitosis with haploid set
Prophase II
Metaphase II
Anaphase II
Telophase II

21. 4 Haploid cells Gametes

22. Meiosis begins by replicating the chromosomes
This step is identical to mitosis

23. The homologous chromosomes then pairs
Centromeres
Do not split
At meiosis I

24. Centromeres Do not split At meiosis I Meiosis I is reductional 2n = 2C

25. Centromeres
Do split
At meiosis II

26. Meiosis 1st division: reduction from diploid to haploid number of chromosomes two haploid cells

27. Crossing over
Homologous chromosomes
Diploid to haploid
Haploid cells
Diploid cells
Homologous chromatids

28. MITOSIS Somatic cells MEIOSIS Cells in sexual cycle
1 cell division:
2 daughter cells 2n 2n
MEIOSIS
Cells in sexual cycle
2 cell divisions:
4 product of meiosis n n 2n n n
n=chromosome number

29. Mitosis
Conservative process:
Daughter cells genotypes identical
to parental genotypes
Meiosis
Promotes variation among the product
of meiosis (crossing over)

30. 2 meiotic 30 mitotic 15 years divisions Puberty 4 mitotic spermatids
spermatozoa
spermatids
15 years
Puberty I II

31. oogonia X Bearing sperm egg ZYGOTE 2n 2n 2n Mitoses
Growth and differentiation
of organs and tissues 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n 2n
Somatic cells 2n
Female germ line 2n 2n
Proliferation of gonial cells 2n 2n 2n 2n
oogonia

32. Primary oocytes Meiosis I Secondary oocytes Polar body Meiosis II
fertilization n
Egg + 3 polar bodies

33. Female meiosis Birth: diplotene of prophase I At puberty every month:
maturation = progress to metaphase II, release from the ovary
Penetration of the sperm:
continue to anaphase II

34. Final result Mitosis : two genetically identical diploid cells
from one diploid parent cell
Meiosis :
Four genetically different haploid cells
from one diploid parent cell