1. Meiosis and Sexual Reproduction

2. Meiosis Reduction/Division
Begins after Interphase, when ______ replicates.
DNA
Reduction:
Process takes a ______ cell with two sets of chromosomes and reduces it to a _________ cell with one set of chromosomes
Division
The cytoplasmic division of one cell into _____ cells.
diploid
four
haploid

3. Meiosis: Reduction/Division
Two divisions:
Meiosis I &
Meiosis II

4. Prophase I Unlike Mitosis: Like Mitosis:
Homologous chromosomes group with other homologous chromosomes to form a “tetrad”
A “chiasma” occurs at the point where the chromosomes cross over, detach, and exchange segments of the chromosome
Like Mitosis:
Nuclear membrane disappears
Spindles form
Chromatin condenses into chromatids

5. Metaphase I Homologous chromosomes line up at the metaphase plate.
Microtubules (spindles) attach to the kinetochore of centromere

6. Anaphase I Homologous chromosomes separate.
Sister chromatids remain attached.

7. Telophase I
Two daughter cells are formed with each one containing only one chromosome of the homologous pair.
The daughter cells are now haploid.

8. Meiosis II: Gamete formation
Prophase II:
DNA does not replicate.
Prophase II is just like mitotic prophase.

9. Metaphase II:
All of the chromosomes line up at the metaphase plate.

10. Anaphase II: Centromeres divide
Sister chromatids migrate separately to each pole.

11. Telophase II / Cytokinesis:
Chromosomes revert to chromatin.
Nuclei reform.
Cytoplasm cleaves
Four haploid daughter cells are obtained

12. Summary of Meiosis (video)

13. What is the difference between mitosis and meiosis? (flash)
Based on the image alone, fill in the Venn Diagram comparing and contrasting mitosis from meiosis. Then watch the flash video with your class, and add information to your graphic organizer.