1. Meiosis

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

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

4. Synthesis (S stage)

5. Prophase 1 Similar as mitosis, except… Two Events:
1) Synapsis: Pairing of homologous chromosomes
The four chromatids equal a TETRAD
2) Crossing Over: Exchange of genes

6. Early Prophase

7. Synapsis: Homologous chromosomes align

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

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

10. Cytokinesis divides the cells
Telophase 1
Cytokinesis divides the cells
Each cell contains 1 of the homologous chromosomes (23 total)

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

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

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

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

15. Defined: Production of sperm cells Occurs in male testes
Spermato-
genesis
Defined: Production of sperm cells
Occurs in male testes
Meiosis produces four haploid sperm cells at a time

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

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