1. Meiosis and Nondisjunction

2. Meiosis Definition: Cell division that divides the number of chromosomes per cell in half to produce sperm and eggs

3. Diploid vs. Haploid Diploid Contains two sets of chromosomes (one set from the mom and one set from the dad) Haploid One set of chromosomes

4. Stages of Meiosis Meiosis I Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II

5. Meiosis I

6. Prophase I Each chromosome pairs with its corresponding homologous chromosome to form a tetrad Crossing over (exchange of information between homologous chromosomes) takes place

7. Prophase I

8. Metaphase I Homologous chromosomes pair together and line up down the middle of the cell

9. Metaphase I

10. Anaphase I The homologous chromosomes are pulled APART to opposite ends of the cell

11. Anaphase I

12. Telophase I and Cytokinesis Nuclear membranes form The cell separates into two cells

13. Telophase I and Cytokinesis

14. Meiosis II

15. Prophase II

17. Metaphase II

19. Anaphase II

21. Telophase II and Cytokinesis

23. Nondisjunction Definition: When gametes have an abnormal number of chromosomes When this occurs: Meiosis

24. Chromosomal Disorders due to Nondisjunction 1) Down Syndrome 2) Klinefelter's Syndrome 3) Turner's Syndrome

25. Down Syndrome "Trisomy 21" Characteristics:

26. Klinefelter's Syndrome Characteristics:

27. Turner's Syndrome Characteristics: