1. Meiosis

2. Quick review: identify this stage of the diploid cell cycle.
Prophase

3. Quick review: identify this stage of the diploid cell cycle.
telophase

4. Quick review: identify this stage of the diploid cell cycle.
anaphase

5. Quick review: identify this stage of the diploid cell cycle.
metaphase

6. Quick review: identify this stage of the diploid cell cycle.
interphase

7. Meiosis Meiosis
Defined: Process where the chromosome number is reduced by half
Gametes created (egg & sperm)
End Result: Four Haploid Cells

8. Interphase
Same process (G1, S, G2)
Chromatin duplicated

9. Synthesis (S stage)
Chromatin strands duplicated

10. Prophase 1 Similar as mitosis, except… Two Events:
1) Synapsis: Pairing of homologous chromosomes
Dad’s #1 chromosome pairs with Mom’s #1, etc…
The four paired chromatids equals a TETRAD
2) Crossing Over: Exchange of genes

11. Early Prophase
Chromosomes form
Nucleus dissolves

12. Synapsis tetrad tetrad
Spindle fibers pull homologous chromosomes together
tetrad

13. Homologous chromosomes (tetrads) align along cell equator
Metaphase 1
Homologous chromosomes (tetrads) align along cell equator

14. Homologous chromosomes are pulled apart to opposite ends
Anaphase 1
Homologous chromosomes are pulled apart to opposite ends
Tetrads separated

15. Each cell contains 1 of the homologous chromosomes
Telophase 1
Each cell contains 1 of the homologous chromosomes
In humans = 23 chromosomes
Cytokinesis divides the cells

16. Note: No new DNA was created (no 2nd interphase)
Prophase 2
Same as mitosis
Note: No new DNA was created (no 2nd interphase)

17. Remaining chromosomes are aligned at cell equator
Metaphase 2
Remaining chromosomes are aligned at cell equator

18. Sister chromatids are pulled to opposite ends
Anaphase 2
Sister chromatids are pulled to opposite ends

19. Telophase 2
Nucleus reforms on the four new cells
Chromatids uncoil
Cytokinesis divides the cells
End Result: Four haploid cells

20. Defined: Production of sperm cells
Spermatogenesis
Meiosis 1
Defined: Production of sperm cells
Occurs in male testes
Meiosis produces four haploid sperm cells at a time
Meiosis 2
Spermatogenesis

21. Oogenesis Defined: Production of the egg cell (ovum)
oocyte
Oogenesis
Meiosis 1
Defined: Production of the egg cell (ovum)
During meiosis I: Cytoplasm distributed unequally
After meiosis II:
1 cell matures
3 “Polar Bodies” dissolve
Meiosis 2
Oogenesis

22. Mitosis Meiosis Division resulting in gametes
Ex: Sperm and Egg cells
End Result: 4 Haploid cells (n)
Importance: Reduces the gamete chromosome number by half
Division of somatic cells
Ex: Blood cells, skin cells, nerve cells…
End Result: 2 Diploid Cells (2n)
Importance: Replaces aging cells
Importance: Form of asexual reproduction