1. Cell Reproduction
Mitosis & Meiosis

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3. Cell Cycle

4. Sexual Reproduction
Meiosis

5. Sexual Reproduction
A type of reproduction in which two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new organism with a unique identity.

6. Sexual reproduction results in a great variety, or diversity, of offspring.

7. Meiosis
The nucleus divides twice
Meiosis I
Meiosis II

9. Interphase
DNA is duplicated

10. Prophase I
DNA shorten & thicken
Forms chromatids / chromosomes

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12. Metaphase I Copied chromatids / chromosomes line up in middle of cell
Centromeres attach to spindle fibers

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14. Anaphase I Chromatid pairs are pulled apart Move to ends of cell
They DO NOT separate
Move to ends of cell

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16. Telophase I
Cell divides
No further replication of hereditary material

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18. There are now two cells. Both cells have full sets of genetic material (chromosomes)

19. Prophase II Similar to mitosis Starts with TWO cells instead of one
Spindle fibers appear

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21. Metaphase II
Duplicated chromatid / chromosomes line up in middle of cell
Spindle fibers attach to centromeres

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23. Anaphase II Centromere divides
Chromatids separate & move to ends of cell
Chromatids are now individual chromosomes

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25. Telophase II Spindle fibers disappear
Nuclear membranes form at each end of cell
Cells divide
Results in 4 cells
Each with ½ the original number of chromosomes

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27. Meiosis Animation

28. In summary: Meiosis Two cells form during meiosis I
In meiosis II, both of these cells form two cells
The two divisions of the nucleus result in four sex cells (gametes)
Each has one-half the number of chromosomes in its nucleus that was in the original nucleus