1. 12/17/14 Objective: Meiosis

2. Produces sex cells (egg and sperm) Produces 4 cells with HALF the normal chromosome number How many chromosomes do human body cells have? How many chromosomes do human sex cells have? (egg and sperm) How the heck does that happen?????

3. Gametes= sex cells that have HALF the normal number of chromosomes (human= 23) Somatic Cells= body cells that have full set of chromosomes (human = 46)

4. -Haploid (n): a cell with half the normal number of chromosomes (gametes) -Diploid (2n): a cell with full set of chromosomes (somatic cell)

5. Fertilization: joining of egg and sperm Zygote: fertilized egg

7. Homologous Chromosomes Same chromosome, one is from mom, one is from dad

8. Downs Syndrome

9. Prophase I: -Spindle forms, chromosomes condense nuclear membrane disappears

10. Genetic Variation Crossing Over: occurs during Prophase I where homologous chromosomes line up and exchange pieces creating genetic variation

11. Metaphase I: Homologous chromosomes line up at the middle

12. Anaphase I: Homologous chromosomes separate and move to poles

13. Telophase I: 2 daughter cells are formed (chromosomes are still duplicated)

14. Prophase II: Spindle forms in daughter cells, nuclear membrane breakdown

15. Metaphase 2: Sister chromatids line up in the middle of cell

16. Anaphase II: Sister chromatids separate and move to poles

17. Telophase II: Cells split producing 4 haploid daughter cells that are ALL GENETICALLY DIFFERENT!

18. Meiosis Sour Straws 1. Maternal and Paternal Homologous Chromosomes

19. Meiosis Sour Straws

20. 2. Crossing Over – Chromosomes exchange sections of DNA

21. Meiosis Sour Straws 2. Crossing Over – Chromosomes exchange sections of DNA

22. Meiosis Sour Straws 3. Meiosis I: Homologous Chromosomes separate

23. Meiosis Sour Straws 4. Sister chromatids separate to form four unique gametes

24. Meiosis Sour Straws