1. Boo-Yah Biology! Meiosis Molecular Biology Sumner HS

2. Quick Mitosis Review Mitosis important in growth & repair Produces genetically identical daughter cells. DNA replicated in S phase Copies divided into daughter cells during mitosis (PMAT) & cytokinesis. Daughter cells have the diploid number of chromosomes. (humans = 46, or 23 pair) http://www.youtube.com/watch?v=O3_PNiLWBjY

3. Meiosis Making Reproductive Cells (Sexual Reproduction)

4. Meiosis Fundamentals Meiosis is a process of cell division that reduces the number of chromosome sets from diploid to haploid, producing 4 cells. Takes place in two sets of divisions, meiosis I and meiosis II It is this process that organisms use to make sperm and egg cells

5. Meiosis Fundamentals Chromosomes replicate once. Two consecutive nuclear divisions (similar stages to mitosis) Meiosis 1 Meiosis 2 Results in four haploid cells. Reduces Chromosome number in half.

6. Meiosis Fundamentals Why do we want reproductive cells to be haploid?

7. Two stages of Meiosis Meiosis I Reduces the number of chromosomes from 4n to 2n, producing 2 cells. Homologous chromosomes separate Meiosis II Sister chromatids separate Produces four haploid (n) daughter cells

8. Chromosome Accounting

9. 9 Regular human body cell = 46 total chromosomes The total number of chromosomes in a regular cell is the diploid number (46 in humans). Or 2n = 46 Or 23 pairs The number of chromosomes received from each parent is the haploid number (23 in humans) Or n = 23 Or 23 total

10. 10

12. 12 Chromosomes and the Cell Cycle During G1 = 2n = 46 During S & G2 = 4n = 92 (DNA is replicated) After Cytokinesis = 2n = 46 Mitosis produces genetically identical cells.

13. Organism Life Cycles At sexual maturity, the ovaries and testes produce haploid gametes by meiosis. n = 23 Not genetically identical to parent cell due to only having half of the total chromosome set During fertilization these gametes (sperm and ovum) fuse, forming a diploid zygote The zygote develops into an adult organism

14. Life cycle

15. Homologous chromosomes What is a homologous chromosome? The pair of chromosomes from each parent Ex: Homologous chromosome 1: 1 from Mom and 1 from Dad

16. Homologous Chromosome What is a homologous chromosome? The pair of chromosomes from each parent Ex: Homologous chromosome 1: 1 from Mom and 1 from Dad

18. The human genome: http://www.ornl.gov/sci/techresources/Human _Genome/posters/chromosome/chooser.shtml http://www.ornl.gov/sci/techresources/Human _Genome/posters/chromosome/chooser.shtml Meiosis: http://www.youtube.com/watch?v=kVMb4Js99t A http://www.youtube.com/watch?v=kVMb4Js99t A

19. Meiosis: The Steps

20. The Steps of Meiosis I Interphase Chromosomes duplicate (4n) Prophase I Homologous replicated chromosomes pair forming tetrads (four chromatids) and exchange gene segments = crossing over

21. Steps of Meiosis I Metaphase 1 Tetrads line up on cell equator Spindles attached to centromere

22. Steps of Meiosis I Anaphase I Homologous chromosome pairs separate Sister chromatids still attached

23. Steps of Meiosis I Telophase I/Cytokinesis New nuclei form Cytokinesis produces two non-identical diploid cells Chromosomes still as sister chromatids.

24. Steps of Meiosis II Prophase II Much like prophase in mitosis Preparation for division

25. Steps of Meiosis II Metaphase II Homologous pairs line up on the metaphase plate (equator) Spindle attaches to centromere

26. Steps of Meiosis II Anaphase II Sister chromatids separate Pulled to opposite ends of the cell.

27. Steps of Meiosis II Telophase II/ Cytokinesis New nuclei forming New cells are haploid, not diploid Cells divide Four non-identical daughter cells formed.

28. Meiosis Accounting During G1 = 2n = 46 During S & G2 = 4n = 92 (DNA is replicated) After Cytokinesis I = 2n = 46 After Cytokinesis II = n = 23

29. Meiosis animation http://www.cellsalive.com/meiosis.htm

30. Now we dance! Two groups: mitosis vs. meiosis Resources: steps of mitosis & meiosis Major roles: chromosomes, membranes Prepare to create a “dance” showing how your style of cell division works.

31. The Big Picture

33. Comparison

34. Mitosis/Meiosis Animation Mitosis vs. Meiosis: http://www.youtube.com/watch?v=C6hn3sA0ip 0&feature=related http://www.youtube.com/watch?v=C6hn3sA0ip 0&feature=related